A young woman named Kate (Emilia Clarke) has been continuously unlucky, leading a life that is on the verge of falling apart. When she accepts a job dressing as an elf at a year-round Christmas store owned by "Santa" (Michelle Yeoh), she randomly meets Tom (Henry Golding) and her life takes an unexpected turn.
Tom sees through Kate's misfortunes and personal failings, offering unsolicited life lessons. Tom shows up whenever she needs him, eventually helping Kate break her bad habits and get her life back on track.