Archer’ season 4 braves unfriendly seas for its twelfths and penultimate episode of the year “Sea Tunt: Part 1,” as Cheryl's brother Cecil ('Bob's Burgers' Eugine Mirman) leads the ISIS crew on an expedition to recover a sunken hydrogen bomb, but the group quickly finds he has more sinister motivations.

Last week’s ‘Archer’ episode “The Papal Chase” saw Archer, Lana and Pam undertaking a mission to the Vatican to protect the Pope from an assassination attempt, realizing Archer’s servant Woodhouse to be an exact double for the Holy Father, so does “Sea Tunt: Part 1” sink under its own weight?  Is ‘Archer’ season 4 diving toward its deepest season yet?

Read on for your in-depth recap of everything you need to know about ‘Archer’ season 4 episode 12, “Sea Tunt: Part 1!”

Malory calls the team into her office for “fantastic” news, namely that a B-52 bomber carrying a hydrogen bomb recently crash landed into the Atlantic ocean. Hoping to recover the bomb before Russia does, Malory plans to return the bomb to US authorities, for a sizable reward of course, which Lana points out is tantamount to ransom. Overhearing, Cheryl begrudgingly announces that her deep sea researching brother Cecil can lend his research vessel, and that he happens to be standing right there.

Aboard Cecil’s luxurious chopper, piloted by his loving-yet-shrill vegan wife Tiffy (Kristen Schaal), Pam gorges herself on vegan shrimp while Archer mixes drinks, and Lana wonders what Cecil gets out of aiding ISIS in the mission. Meanwhile, Cecil makes time for a private chat with Malory, hoping to learn more about Cheryl’s apparent psychotic episodes. Cheryl watches her brother’s actions in secret, annoyed to hear the ominous non-diegetic music.

Pam continues stuffing her face in spite of her soy allergy, while Cheryl postulates that Cecil hopes to get ISIS testimony on record, and get a conservatorship over her inheritance. Meanwhile, Lana presses on Cyril and Ray the immorality of Malory’s hydrogen bomb ransom, though they only worry about what cut of the bonus they might receive.

Cheryl enters the cockpit and attacks Tiffy, while Malory and the others see that Pam has begun choking from her allergy. Still drinking, Archer attempts to perform an emergency tracheotomy, but Pam resists and demands they get the epi-pen from the cockpit. Lana and Cecil continue trying to break into the cockpit as the chopper veers out of control, and even Archer finds the door to be bulletproof.

Shot in the leg from ricochet, Cecil admits that Cheryl’s fears were true, and there was never an actual hydrogen bomb to recover. Archer races to save Pam, for which she attacks him over his initial suggestion, and Lana throws Cecil into the room. Cecil admits that the real reason he brought the group to his research lab was that the mad “Captain Murphy” (‘Mad Men’s Jon Hamm) of his undersea lab has demanded the world ‘s leaders stop polluting the ocean, and has prepared to launch nerve gas missiles at US locations if they don’t bend to his demands.

Multiple-episode 'Archer' events unusually make for its best episodes, even if the journey there in "Sea Tunt: Part 1" clearly feels reminiscent of the space-faring adventure of last year, complete with a famed AMC actor voicing the villain. Unlike last year however, 'Archer' season 4 hasn't built toward much of an over-reaching conflict with recurring villains Barry and Katya, unless they somehow present as part of Captain Murphy's plot. Instead, "Sea Tunt: Part 1" gives some well-deserved spotlight to Cheryl, well-colored by the predictably-fantastic Judy Greer. The jokes land, with fine-characterization all around, but we can't help feeling much of the finale's action will end up overcrowded as a result, diluting very little into tonight's episode.

What say you? Did you get your fill of spy-spoofing ‘Archer’ action?  What was your favorite gag from “Sea Tunt: Part 1?” Join us next week for another all-new ‘Archer’ recap of season 4′s finale episode “Sea Tunt: Part 2” on FX!