Walter (David Hyde Pierce) is a widowed college professor. He returns to NYC and finds a pair of undocumented immigrants (Tarek and Zainab) "squatting" in his apartment. Instead of calling the cops, Walter says they can stay temporarily, though they're reluctant because they don't trust him. Tarek teaches him to play the djembe and they develop a friendship; Zainab is reluctant to get close to Walter. When Tarek is arrested by ICE and Walter witnesses it, Walter uses his inherent privilege to attempt to help his new friend and ends up falling in love with Tarek's mother.
Someone of lesser character might have tried to push these people out of his life and ignore the situation. Zainab (probably the most interesting character) even questions Walter's motives for helping them. (Walter demonstrates subtle racism in a few instances at the start of the show and he evolves as the evening progresses.) It's, above all, a story of an "everyman," unsatisfied with work and mourning his wife, who gets roped into a complicated situation that shows him how broken this system is for immigrants trying to start a new life in America.
In the end, Walter doesn't save anyone, and no character has a happy ending. Bleak, but anything happier might have been too "musical theatre quaint" considering the realities of life for immigrants in America.