So it was sexually transmitted after all.  Well, now you know to keep away from those Castor boys.

The episode begins in Sarah’s cell.  She walks out of her holding room and enters the courtyard, only to find it empty.  Upon hearing laughter, Sarah explores and ends up finding, of all people, Kira.  Sarah follows her daughter until it suddenly gets dark, but they’re able to take cover in a tent.

And that’s where Sarah enters an examining room and sees both her body on a bed, Rudy next to her on another.  Connected by a vial, the two rest as blood works its way from Rudy to Sarah’s neck.

Sarah awakens, but finds that she still has the same bandaged point on her neck.

Paul meets with a man, played by Tom Barnett, and gives him the black book containing research Castor soldiers took on their companions.  Such research on civilians is unsanctioned and has nothing to do with Castor psychology.  The man is willing to pass this to the director, but Paul will need more proof about what Dr. Coady is doing.  Until then, they can’t act.

Mrs. S and Felix have a Skype call with Kira, who is doing well, but wonders if her mother is mad at her.  When the call ends, Felix lets his real feelings loose: he’s very much worried about Sarah.  It’s been five days and even if S’s people have located Castor headquarters, they still don’t have any new information on Sarah.  As for Gracie, who is just looking for something to do, S assures Felix that Cosima is working on how to counter this disease.

Cosima should probably work on remembering to answer her phone, as Shay points out that she slept through other calls.  Cosima also apparently said the name Sarah while dreaming.

Meanwhile, in one of the most entertaining moments of this episode, Alison and Donnie make it rain in celebration, they wall twerk- they do it all!  Gemma enters and the two remember that they have parental responsibilities.  Well, Donnie does, as he has to drive the kids to karate, while Alison is set to meet with Jason.  Donnie wants to be there.  Yes, he’s a tad savage jealous, but paying this debt is serious business and he wants to play his part.

So Cosima finally shows up late, much to Scott’s annoyance, and learns, much to her surprise, that Delphine has returned.  She got back as soon as she found out that Sarah was missing.  Delphine is now protecting Leda, but Castor remains impenetrable- exactly why Delphine warned Sarah against trying to go after them.  Delphine also reveals that she knows about the retrieval of a Castor brain.  How?  They ran the tissue through this lab, and Dr. Nealon is no fool.

Delphine shows Scott and Cosima something interesting: the same misfolded protein in both the dead Castor boy and Gracie Johanssen.  The two were studied in isolation, though, so there was no reason to compare.  However, Delphine feels that this warrants a follow-up.

Back at the base, Mark checks in on Sarah, who is shaking, burning up, and wants out, even if that just involves a gun and car.  She also calls Paul the worst, as she doesn’t even know where he stands.  Dr. Coady enters and tells Paul that Sarah will be fine- she’s just suffering from the effects of an anti-inflammatory.  Sarah protests that something else was done to her and that Rudy was present, but Coady leaves with Paul to fill him in on the current situation.  If the desert doesn’t get Helena, then Rudy will.

Speaking of, Helena runs through the desert and collapses from exhaustion.  The scorpion taunts Helena until she decides that she’s hungry.  Bye-bye, scorpion.

Paul asks Dr. Silva about Sarah’s condition, but Silva says that he wasn’t there.  Sure, Coady usually shares what’s going on, but things have changed since Paul left.  When he did, everyone was trying to cure sick soldiers.  One day, Rudy came back from leave and had a sick girl with him- bloodshot eyes and everything.  Dr. Coady cured her.  Silva didn’t think much of it, but then science took a turn.

Things got more secretive.  The boys were told to record intimate contacts, meaning take hair samples, and Silva would test them for genetic purposes.  Though Coady says that it’s for security purposes, Silva thinks that it’s really to get baseline numbers.  Either way, Coady keeps her materials in her quarters.

Delphine tries to make small talk with Cosima about her missing work and whether anything is wrong, but Cosima assures Delphine that there’s nothing she needs to know.  Felix and Gracie arrive, though Felix needs some help from Scott, and by that, I mean that Felix wants to be taken to Rachel for some Castor information.  Though Scott isn’t supposed to know where Rachel is, Felix is desperate at this point.

On base, Paul talks with Mark, who reveals that he fell in love with Gracie Johanssen.  Paul needs Mark’s help with some unofficial business.

Alison meets up with Jason to pay him in full, meaning that her part is done, but she wants to take this business to the next level.  But then Donnie rolls up in a fine-ass car that only cost him $10,000, which he paid in cash.  Donnie doesn’t know the meaning of the word conspicuous, apparently.  Plus, that could attract the attention of the authorities.  Donnie doesn’t think cars are conspicuous since they’re everywhere.  He makes a persuasive argument.  Jason tells the two that they need a front since selling garage made soap won’t cut it.  Luckily, Alison has a business plan she’s been mulling over for awhile.

Back at the base, Mark gives Paul a key.  The two have five minutes.

Over at DYAD, Gracie learns that the protein is in her bloodstream and is similar to something in one of Mark’s brothers.  It’s possible that this is how the Castor clones transfer it to other systems.  The protein can have different effects on different people.

As this happens, Paul enters Coady’s quarters and, after going over some files, learns that the disease is contagious and sexually transmitted.

Paul confronts Coady to place her under arrest for sterilizing women.  Coady isn’t worried and even admits to giving Sarah the Castor pathogen.

In her dreams, Sarah follows a girl- I think the same girl from the end of Season Two- and ends up in Mrs. S’s place, where she meets Beth, who has been thinking about the day Paul moved in.  He had two suitcases to his name, which should have been a red flag, but she was gaga for him.  Though Sarah barely got to know Beth, Beth tells Sarah that she doesn’t get to miss her.  Sure, Sarah keeps stumbling and took over Beth’s life, but we do terrible things for the people we love.  It’s time for Sarah to stop asking who and start asking who.

Paul calls the man from the bench about the evidence and medical records that go back two years.  He also informs the man that Coady is confined to quarters and the camp is on lockdown.  Good.  Paul will now need a formal Removal of Command order and an extraction team.  The man will now tell the director, hopefully, but he can have a team there in six hours.  Rudy’s patrol is still out and searching for Helena, though.

Rachel’s painting time is interrupted by the arrival of Felix, who wants to know about Castor and Sarah’s whereabouts.  But Rachel’s condition and inability to speak properly means Felix isn’t getting the information he needs fast enough.  He paints on Rachel’s eye patch and yells that he wants to know where his sister is, though Rachel tells Felix that she wants to be taken out of here.  As Felix and Scott leave, Scott notices some diagrams on Rachel’s paintings.

Alison shows Donnie and Jason her potential store front: her mother’s store, Bubbles.  It’s a reputable local business and is centrally located for distribution.

Out in the desert, Rudy receives a call.  There’s a situation at the base.

Once Gracie and Cosima have left, Delphine watches footage of Shay and Cosima- as well as having tons of photos of the two- and sees that Cosima originally wanted to slow things down with Shay, but now just wants to make out for several hours.  However, that’s sidetracked by a call from Scott, who brings up the weird symbols in Duncan’s book: Rachel may have the code.

Paul fills Sarah in about the human sterilization trials, but Sarah hasn’t shown any of the same symptoms as the other women.  Sarah asks Paul if he loved Beth, and he just responds that what happened with Beth is something that he’ll carry forever.  They were looking for a cure and thought that DYAD had answers.

Paul and Sarah speak with Dr. Coady, who is surprised that Sarah isn’t hemorrhaging.  Coady knew that Sarah would beat it because Castor and Leda have the same disorder.  It attacks the men’s brains, but the women’s epithelial tissue.  Due to Sarah’s fertility, she can fight off the disease.  Coady is infecting innocent women to understand.  She didn’t put it in the boys- she just found it, meaning that it was engineered.

Paul realizes that this is a field weapon that could be isolated to develop in other forms.  Exactly.  Coady is willing to do this because it could apparently end wars in a single generation without spilling a drop of blood.  But who wants it?

A truck returns to base.  The lone soldier says that Rudy is returning on foot, but Rudy is actually underneath and slips off on another direction.  He kills one soldier and frees Miller.

Sarah and Paul meet with Mark.  Paul calls the man, who he knows isn’t being completely upfront with him.  Paul lies and says that Rudy’s patrol is still out in the desert.  No problem.  They’ll be waiting.  Paul then tells Mark to return to his quarters.

So Paul and Sarah make their way through the base, but run into Miller.  A fight breaks out and Paul is able to snap Miller’s neck, but not before Miller manages to stab Paul a few times in his stomach with Paul’s own knife.

The two keep on moving until they reach a shaft.  Sarah crawls in, but Paul does not.  Instead, he tells her that the tunnel comes out in a garage.  Take a jeep and go northwest.  Before leaving, Paul tells Sarah that it was never Beth that he loved.

A bit later, Coady and Rudy find a bleeding, dying Paul, who wants the women cured.  Coady is insulted and shoots Paul for suggesting that she turn her back on science that rewrite the nature of humankind.  However, Paul has a consolation prize in the form of a grenade that he drops.

As Sarah continues her escape, the environment around her shakes due to the explosion.  Though she’s slowed down, she’ll get some help in the form of Helena.  That was a tad convenient.

Well, we got quite a lot in this episode and spent time with pretty much most of our main players.  Credit where it’s due, I never thought that this episode felt overstuffed in an attempt to devote time to all of the clones and their companions.  The portions with Alison were brief, but mostly felt like set-up for confrontations and scenarios that will come in later episodes, while the bulk of the conflict went to Sarah and Paul or Cosima’s situation.

Plus, we got a sort-of revelation regarding the transmitted disease.  Given how Gracie showed signs of it only some time after she and Mark consummated, it could only have been sexually transmitted unless the Castor clones can just infect you through breathing or sheer will alone.

But the plot involving the Castor clones only thickens, as Dr. Coady is just one pawn in a much larger puzzle.  Why does someone else need this disease weaponized?  And what are the odds that it can do everything that Coady predicts it can do?  There are a lot of unanswered questions surrounding this mystery, but I wonder how much evidence and research is left, given Paul’s finishing move.

Let’s go right to Paul, then.  The deeper the man got, the more dangerous it was for him.  Until the very end, he still remained loyal to Sarah, despite his tactics.  And I like how his true desire was to find cures for the Castor clones, but people higher than him had other ideas.  I wouldn’t say it’s as big of a redemption as some have made it out to be because he was still involved in Helena being brought to Castor in the first place, but at least he did sacrifice himself to hopefully destroy Coady’s work and give Sarah time to escape.

Sticking with explosive scenes, Felix raging out at Rachel was, to me, a bit unnerving since Rachel isn’t in any position to defend herself at all.  However, this rage came off as more of Felix’s growing desperation for any information on Sarah.  She’s worlds away, has no way of being in touch, and Felix is powerless to do anything to help.  It shows his devotion, but also his willingness to get his hands dirty by toying with Rachel.  Yet, Rachel potentially knowing the code may be a way to bring her back in the game, despite her current state.

It really is convenient for Delphine to return just after we’re introduced to Cosima’s potential new love interest.  I do hope that there’s a good reason behind her spying on Cosima and Shay, because I don’t really have any interest in a short-sighted jealousy storyline.  Delphine is very calm and collected that she seems like the type to be above jealousy, especially since she’s the one who broke off the relationship.  Who knows?  Maybe there’s a reason for her spying.  If it’s jealousy, though, I don’t find it compelling.

Alison and Donnie got to have some more fun with their separate storyline.  The two making it rain was over the top, but it didn’t seem too out of character for an already odd couple, wall-twerking aside, though that did give Maslany a chance to be versatile.  Donnie suggested in an earlier episode that Alison could go back to working at Bubbles, and it looks like we’re getting some payoff to that, even if it just a front.

Helena only shows up in two scenes, one to rid herself of the scorpion and another when she appears to Sarah.  Given how she ended the previous episode, I would like to have seen her do some more grappling with her decision to leave Sarah behind.  As is, it only seems like the two are reunited for the sake of having them together again.  Because of the big choice she made, I just don’t think she’s had a lot of time since then to think about it.

Sarah’s dreams seem to be a side-effect of the pathogen, which I don’t fully understand, but at least she got to have another moment with Beth, who helped with a pep talk on asking the right questions when Sarah seemed to have given up.  She still has tons of questions, but now she has the quest of finding out who originally created the disease and why someone wants to weaponize it.  Plus, she won’t be alone.

“Certain Agony of the Battlefield” was a pretty good send-off for Paul as he made one last ditch effort to derail Dr. Coady’s work.  The revelation that Rachel may know the code is sure to bring her back into the main picture as the other clones continue to try and make sense of what the hell is happening.  Should be fun.