Castle (2009)

S7E6 The Time of Our Lives

When a murder case unfolds, Castle finds himself in a bizarre alternate reality where he has never crossed paths with Kate Beckett. Determined to return to his original life, he must persuade Beckett, Esposito, and Ryan—who are now unfamiliar faces—to allow him to join their investigation. As he navigates this strange new dynamic, the experience ultimately motivates Castle and Beckett to consider taking their relationship to the next level and planning a wedding.