During their first night aboard, Ruby's mind is consumed by sex, while Billy probes for personal details she's reluctant to give up. Comforted by the fact that her husband believes she's on a weeklong yoga retreat – and determined to make Billy jealous – Ruby brazenly connects with Derek, a stranger on the train. Meanwhile, Billy works to shake a persistent figure from his past.

Ruby and Billy decide to spend a day in Chicago before making any rash decisions about their next moves. As the two anxiously await check-in at a lavish hotel, Ruby meets an exciting woman at a department store, while Billy tries to handle a relentless Fiona. Later, Billy comes clean about what drove him to run.

Back on the train, Ruby seeks guidance from a new friend and gets a wakeup call from home that leaves her shaken. Meanwhile, Billy continues to lie about Fiona, who raises the stakes to get what she wants.

A dramatic detour finds Ruby and Billy in unknown territory as they’re forced to make a life-changing decision. As Ruby tries to keep everything together and get back on course, she and an emotional Billy seek the help of an amiable local taxidermist, Laurel.

Stranded in the middle of nowhere, Ruby and Billy argue about what to do next. Each affected by the other's desperation, the two must come together to confront their actions. Meanwhile, Laurel makes a gruesome discovery and receives an eventful visit from Detective Babe Cloud.

With the end of their journey approaching, Ruby and Billy consider their future together. Are they finally being honest with each other? Babe and Laurel are forced together as they follow a new lead. Season finale.