Merry Christmas is a crime thriller based on Frédéric Dard’s Le Monte-charge which is set on a fateful night of Christmas Eve in Mumbai in the 80s where Albert (Vijay Sethupathi) has just returned to Mumbai from Dubai after seven years and gets to know that his mother expired a year ago. While strolling down a street in the city of Mumbai with a heavy heart, he treats himself at a lavish restaurant where he crosses paths with Maria (Katrina Kaif), who has stood up by her date because she brought her daughter along. Soon Maria and Albert get acquainted with each other which leads to the former taking the latter into her old-fashioned apartment, only to later find himself caught up in a crime scene. He can escape any moment, but he decides to stay and help Maria figure out things. What happens next forms the remaining part of the plot.