With all the pot and prostitutes floating around Amsterdam, this otherwise normal urban setting can seem like a refracted version of reality, observes a character early on in Adam Rapp’s “Red Light Winter.” And so it is with this play, where memories are selective, friendships are booby-trapped and love is punishingly unrequited. Matt (Christopher Denham as the bookish, self-deprecating brooder) and Davis (Gary Wilmes, the prick with the offhand charisma) are American pals—post-collegiate, pre-midlife crisis—hostelling in Amsterdam’s Red Light District. Directed by Rapp in a world premiere at the Steppenwolf Garage, the somewhat autobiographical Act One, a nearly perfect blend of serrated humor and exposed-vein pathos, concerns their dalliance with a beguiling French window whore named Christina, whom Davis has brought back to their room as a gift for Matt, a born-again virgin in need of a mercy fuck, or at least a mercy cuddle. (Word to the prudish: the staging is fully graphic.) But first, some small talk amongst the three, which evolves into a kind of raconteur one-upmanship between Davis and Matt. At these moments, Rapp’s writing is nimble and ear-catchingly funny, as are the performances of Wilmes and Denham, who suggest a credibly warped and complex bond that seems based on complacency and a sadomasochistic urge. Less compelling is Christina’s personal saga, despite her meaty back-story and Lisa Joyce’s artful transition from provocative to plight-ridden. The second act takes place a year later in New York, where the three unceremoniously reunite in a trifecta of unrequited love, and it is here that the play loses its way. Something about the second half doesn’t square with the first; Matt, Davis and Christina become flattened into two-dimensional caricatures of their former selves. Amidst all the talk of unrequited love, Rapp has inadvertently devised an unrequited play. (Nina Metz) “Red Light Winter” plays at The Steppenwolf Garage, 1624 North Halsted, (773)761-4477, through July 24.