Burt Gurney (Channing Tatum), the dancing (and possible gay), sailor is the communist infiltrator in the studio. His band of Marxist and blacklisted writers kidnapped Baird Whitlock (George Clooney). Eddie Mannix (Josh Brolin) pays the $100,000 ransom to get Whitlock back.
A Soviet submarine surfaces off the coast of the beach house where Whitlock is being held. The writers row Gurney out to board the submarine and hand him the briefcase full of ransom money. But, as Gurney is getting on the submarine, his poodle, "Eagle", leaps off the rowboat to join him. Gurney grabs the dog, let's the briefcase drop into the ocean and sink, and disembarks on the submarine as the stunned rowboat full of writers looks on.
Hobie Doyle (Alden Ehrenreich) finds the beach house that the writers vacated and rescues Whitlock. Whitlock has suffered a bit of brainwashing/Stockholm Syndrome and attempts to convince Mannix of the benefits of Communism. Mannix slaps some sense into Whitlock and Whitlock goes back to finish Hail, Caesar! Mannix rejects the offer to work at Lockheed and stays with the studio.
Other plot threads include:
A mirroring of the Loretta Young/Clark Gable pregnancy and the old Hollywod morality codes, where pregnant, unmarried, synchronized swimmer, DeeAnna Moran (Scarlett Johansson) marries Joseph SIlverman (Johnah Hill), who agrees to be the foster father of her baby.
Also, since Gurney was the source for Thora Thacker's (Tilda Swindon) story about Whitlock's homosexual relationship with director Laurence Laurentz (Ralph Fiennes), Mannix is able to convince her not to break the story because Gurney was a Communist and using a Communist source would destroy Thora Thacker's career.
Thanks Evil Ed!