In Susan Loesser’s 1993 biography of her father, the Tony-winning songwriter Frank Loesser, she parses the etymology of her dad’s late-’40s pop standard “(I’d Like to Get You on a) Slow Boat to China.” Loesser’s great gift as a lyricist was the compression of complex emotions into insinuating innuendo; think of the coy, call-and-response seduction of “Baby, It’s Cold Outside,” in which metaphorical decorum gets stretched to the breaking point.

For “Slow Boat,” Loesser borrowed a phrase common to poker players describing somebody unable to extricate themselves from a run of bad luck yet unwilling to fold—a loser whose agony is drawn out. Recognizing the kinship between gambling and romance—and the exquisite ache of a situation with a high-stakes yet indeterminate outcome—he crafted a love song with possessive undertones, whispered in the barely suppressed language of conquest and control:

Out on the briny
With the moon big and shiny
Melting your heart of stone
I’d love to get you
On a slow boat to China
All to myself alone

The first image in The Master is of the ocean, of massive waves churning both of their own implacable accord and also in response to the presence of a vessel—an American military transport tracing a slow, steady swath through the water. Given the subsequent revelation of time and place (the Pacific circa 1945) the ship might even be a slow boat to China, subliminally anticipating the deployment of Loesser’s song at the film’s climax, where its performance by a major character for another stands in plangently for their mutual dependency. The singer is Lancaster Dodd (Philip Seymour Hoffman), the founder and frontman of a controversial philosophical movement called “The Cause”; the listener is Freddie Quell (Joaquin Phoenix), a World War II veteran who is the Cause’s most ardent and yet intractable initiate. For several group insiders, including members of Dodd’s family, Freddie’s impulsiveness supersedes his loyalty, making him a liability to a fledgling movement already under scrutiny by the authorities. And yet Dodd, for reasons that are strange even to himself, refuses to let him go.