Merry Christmas narrates the story of a fateful night of Christmas eve where Albert (Vijay Sethupathi) has come back to Mumbai from Dubai, or so he claims, and realises that his mother is no more. Taking a stroll in the city of Bombay (now Mumbai), he goes to treat himself at a lavish restaurant. There, his path crosses Maria’s (Katrina), who has been stood up by her date because she brought her daughter along. They exchange quick glances, and meet again inside a theatre. One thing leads to another and Albert ends in Maria’s 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.