In 1930s Los Angeles. Jack Parsons works as a janitor at a chemical factory by day, but, by night, he nurses a secret ambition: to build rockets that will take mankind to the moon. The pressures of his double life are further complicated when Jack and his wife Susan are confronted by a mysterious new neighbor, Ernest Donovan, who appears to be leading a double life of his own.

After Professor Mesulam gives his blessing to the project, Jack and Richard set off to create Caltech's first ever rocketry team. But Caltech's acceptance has come with caveats, and, coupled with Ernest's looming presence, Jack and Susan are feeling more on edge than ever before, desperate to figure out whether Ernest's intentions are evil or not.

Jack’s expert witness testimony at a high profile trial thrusts the rocketry team into the spotlight and helps land them a coveted invitation to The Athenaeum. Meanwhile, Virgil drops off Patty, Susan’s rebellious teenage sister, for a disruptive weekend stay, and Ernest’s wife, Maggie, makes a surprise return. When Jack’s evening at The Athenaeum doesn’t go as planned, Jack seeks out Ernest to blow off some steam and ends up on a dark detour into the Los Angeles underbelly.

A secret return visit to the Agape Lodge leaves Jack wanting more, inspiring him to explore new sexual boundaries at home with Susan, despite her misgivings. Ernest's sudden presence at the Rocketry Team's new desert testing facility has Richard questioning the whole endeavor, until he meets a mysterious woman who helps restore his faith. Meanwhile, Maggie has doubts about Ernest's fidelity.

Susan's concerns about Jack grow after she researches Aleister Crowley and confronts Maggie with the mysterious truths behind this cult religion. Susan's questions leave Maggie at a breaking point, forcing Ernest to confront his inner demons.

When Jack receives a letter from Aleister Crowley, inviting him to ascend to the next degree, the Parsons must decide if Thelema is what they both want for their future. After uncovering the truth about Virgil during her purge sessions, Susan is forced to deal with the chilling revelation back in the real world. Richard and Jack finally find common ground, rallying the Suicide Club for a dangerous final demonstration to the military. For the demo, Jack has all he needs except for one crucial element: Ernest.