The beleaguered physicists in Frank Winter's group finally get some good news on the implosion front in this week's episode of Manh(a)ttan. It's titled "The Understudy," a reference to the fact that Jim Meeks, one of the scientists in Frank Winter's group, has an understudy role in the base camp's upcoming production of Our Town: "Everyone knows the whole show rests on the understudy."

Of course, the understudy when it comes to the Manhattan Project is Winter's implosion design concept, which has taken a back seat to Ackley's Thin Man prototype since the series began. But Frank's team -- minus Helen, who has been transferred to Team Ackley -- still hasn't cracked the problem of controlling the shock wave. Meeks tries for optimism, pointing out that Thomas Edison always took hope whenever he hit a brick wall. Babbit's having none of it: "We didn't hit a brick wall. We hit the Grand Coulee Damn." To add insult to injury, instead of more scientists to help with the problem, they must contend with a couple of janitors lurking on the premises, meaning they can't discuss classified topics when said janitors are present. Frank is not nearly as upset as he should be, causing Babbit to wonder what he's up to.

What he's up to is conducting detonation experiments with Charlie Isaacs and Lazar at the armory, looking for a clue as to how to control the shock wave blast in the implosion bomb. They stand around a vat of water with three small point charges and set them off, watching how the shock wave spreads outward. Frank explains that he envisions 32 "points" around the spherical core of an implosion-type bomb, detonated simultaneously; the trick is how to redirect the shock waves to create a perfectly spherical implosion, which is tantamount to turning all those tiny explosions inside out -- the waves must be concave, not convex. Lazar thinks it quite simply can't be done.

There's nothing like some fun with explosives to get guys to bond; the flinty Lazar even shares his chewing tobacco with Frank and Charlie, although the latter reacts badly to it. Frank and Charlie aren't becoming friends, exactly, but there is some noticeable warming of their frigid bond -- even on the charge of plagiarism. Frank now things that while Charlie may have lifted one idea in his notorious paper on a new nuclear cosmology, the rest of the paper was sound -- a far more sensible and realistic attitude than we've seen previously from Frank.

And when an angry Babbit realizes that Frank and Charlie are in cahoots -- hoodwinking Ackley scientists into working on detonation space calculations -- Frank says, "I've come to trust him [Charlie]." Babbit is still unhappy. Frank may go to prison when he's found out, but Babbit -- already under a cloud of suspicion because he loved a gay Communist physicist -- could face a firing squad. As always, Frank forges ahead for the good of implosion, with little thought to possible collateral damage.

Boys and Their Toys: Lazar (Peter Stormare), Frank Winter (John Benjamin Hickey) and Charlie Isaacs (Ashley Zukerman) testing the waters for shock wave control.

Charlie's paper ends up giving Frank the "Eureka!" moment we've all been waiting for when he reads it later that day. He joins Charlie and Lazar (still playing with explosives) at the armory and says he's figured out how to shape the shock wave using "explosive lenses" and by varying the burn rates of the explosive materials used, exploiting something called the "Munroe effect."

This is, indeed, how the real physicists on the Manhattan Project approached the shock wave control problem. The Munroe effect -- named after a 19th century chemist named Charles Munroe -- describes how blast energy can be focused by a hollow or a void cut into the surface of an explosive. Munroe discovered the effect quite by accident when we was working with a block of guncotton, detonated next to a metal plate. The lettering stamped into the explosive block was also cut into the plate when the charge went off.

Munroe built the first so-called shaped charge in 1894, and it was featured in Popular Science Monthly in 1900, but it wasn't until World War II that it was adapted to nuclear warheads, using a 32-point assembly to create an "explosive lens," just as Frank described. And yes, it is critical to vary the burn rates of detonation to get an expanding wavefront to turn inside out. The Gadget prototype used in the famous Trinity Test, as well as the Fat Man bomb dropped on Nagasaki, combined fast and slow explosives. (Helen specifically mentions Baratol when Charlie tells her they've solved the problem, and that was the slow burn rate explosive used.)

Meanwhile, there is an unexpected visitor to the base camp: Annie Liao, widow of the unfortunate Sid Liao, who was shot for suspected treason way back in the second episode. She shows up at "Post Office Box 1663" and refuses to leave until she speaks to Frank Winter, intent on finding out just how and why her husband died. She gets the sinister Occam instead, pretending to be Frank -- at least at first. His probing questions as to what Sid may have told her, or whether he asked her to pass along any messages to anyone, quickly arouse her suspicion, and she guesses he is not Frank Winter. "There is no one here by that name," Occam says, because is a lying liar-man.

Occam advises her to go home -- via a train ticket the US Government has provided -- and forget all about the past, focusing on her daughter's future instead. Annie demands to see Sid's death certificate and any formal report. She swears she wants the truth. "You want a bedtime story, a fairy tale," Occam counters, but he gives her a sealed file pertaining to Sid's death and tells her he wasn't a hero -- he was a spy.

What this episode needs now is a spot of sex, and we get that in spades with Private Cole Dunlavy and Callie making out in her bedroom. Callie is all for going further -- "I don't think desire is evil" -- but Dunlavy turns out to be the shy, overly moral sort and pushes her away. He asks why she's with him at all, wondering aloud if it isn't just to rebel against her parents, because he shot their friend, Sid Liao. An angered Callie tells him Sid was her friend, too, and tosses him out. Still guilt-ridden by what he has done, Dunlavy tells Meeks that Annie Liao has been on base and will be heading to the train station by bus the next day. If you're thinking his romance with Callie is kaput, think again. She comes to barracks that night and asks another soldier to give Dunlavy a Bible. When Dunlavy opens it to the marked page, Calllie has written in the margins: "I like you because you make me feel that someone's listening." Aw, young love survives.

Abby (Rachel Brosnahan) fixes her lipstock after dallying with Elodie (Carole Weyers) on "Manh(a)ttan."

Things are also still hot and heavy between Abby and Elodie, who engage in the Sapphic delights in a meadow one sunny afternoon. But when Elodie invites her for dinner, Abby is reluctant, admitted that Elodie's husband, Tom, had groped her the last time. Elodie, to her credit, is shocked at this affront to her lover's honor -- more so than Charlie was, frankly. Abby's still in denial about exactly what's going on between, insisting it's not an affair. And when Elodie meets her for a drink in the very public base canteen, Abby tries to end the dalliance.

Their conversation is interrupted by a young married couple who are friends of Elodie and like to trade partners with other couples (a shocked Abby declines their invitation to join them in bed that night). The wife returns a book the Frenchwoman had loaned her (Camus's L'Etranger), which Elodie pointedly describes as being about how "society invents rules to keep us from happiness." She tells Abby that everybody on the project has a secret life: "The difference is you're keeping the secret from yourself." Elodie's mantra is that life is short, and getting shorter given that their husbands are inventing "the end of the world."

That's how Charlie comes home to find Abby reading Camus in the original French -- she did study French at her mother's insistence and is clearly quite proficient in the language, not to mention smarter than Charlie gives her credit for. "You buy gossip magazines for the photo spreads, and suddenly you're reading Beaudelaire?" he says with surprise, clueless about how insulting this is to a woman he presumably loves. Abby tells him she knows he's not really working on a new radar system, but he still won't tell her the true nature of his work. Anyway, Camus changes Abby's outlook. When she returns the book to Elodie, she confesses that she has spent her entire life being "exactly the person everyone expected me to be. I don't even know what I want." But for now, she's okay with wanting Elodie.

Meeks takes advantage of Dunlavy's tip and meets Annie briefly on the bus, telling her he wasn't allowed to call or write after Sid's death -- and he still can't say what they're all working on. But he assures her that no matter what Occam told her, Sid was not a spy. Annie asks him to deliver a message to Frank: "Tell him there's nothing to feel guilty about." She means he shouldn't feel guilty for being the one to bring Sid on board the project in the first place, but Meeks still has questions as to who might have betrayed Sid, and has an inkling it might have been Frank. Later that night, Occam visits him in the otherwise deserted Winter lab and says he, too, has many questions about Frank. Will Meeks realize the truth and betray Frank in turn for sacrificing Sid Liao for the greater good? Or will loyalty win out?

Liza Winter (Olivia Williams) tests her home for radiation on "Manh(a)ttan."

The episode ends with an unexpected twist. Recall that Liza finally got a job on base helping out in Dr. Adelman's clinic. She's called to assist when there is a contamination emergency, which involves scrubbing down the two men affected -- one of whom reveals there have been incidents before. While dumping the contaminated clothing in the bin out back, she notices the stream of waste water pouring into the soil.

Adelman explains the contamination results from the men's work with explosives and the scrubbing is designed to remove all the residue. But he also asks her not to mention the incident to anyone outside the clinic. Small wonder Liza's suspicions increase. She "borrows" the clinic's Geiger counter and scans various items in her own home -- dinner plates, linens cutlery, and so forth -- and is horrified to discover all exhibit radioactivity.

Frank comes home to find her frantically burning all the bedclothes in an oil drum. "It's all poisoned! It's all radioactive!" she insists. But when she rescans the household items in Frank's presence to prove to him she's not imagining things, she doesn't get any readings on the Geiger counter, and breaks down, sobbing. Apparently she really is imagining things.

I admit, I did not see that coming, even with the revelation that Liza has a history of mental illness. The final scene is Frank gently putting her to bed and giving her some of her old medication. We've been led to believe that the purple flower and Liza's dead bees were indications of something sinister, likely related to the radiation that is undoubtedly present in the research labs on base. And maybe there is a risk, but Liza's testimony probably won't matter much if everyone just thinks she's crazy.

Only three more episodes to go! Let the fireworks (both personal and professional) and inevitable collateral damage begin.