Luke has been living out of town and returns to Oakdale for the holidays. He's been alone all this time and can't face going home alone, so he enlists Dr. Reid Oliver to pretend to be his boyfriend just for the holidays. It'd be fun if Luke forces Reid through blackmail or kidnapping and must get creative in making sure Reid doesn't spill the truth to the Snyders.
OR
Reid is going home for Christmas to see his family (if they're still living) or Uncle Angus (to follow canon) after a long absence and can't face going alone so he gets Luke to pretend to be his boyfriend/husband/partner to please (or impress?) his family.
There are so many films like
this, but I don't think I've read a holiday-themed LuRe fic with this plot yet.