Maa is a story about Ambika (Kajol) who is leading a happy life with her husband Shubhankar (Indraneil Sengupta) and daughter 12-year-old daughter Shweta (Kherin Sharma) in Kolkata. For some reason, they don't want to visit Shubhankar's ancestral village, Chandrapur where they have a mansion. But his father's death forces Shubhankar to visit Chandrapur where he dies under mysterious circumstances after completing the final rites. Ambika and Shweta visit Chandrapur on the insistence of the village sarpanch, Joydev (Ronit Roy) as they plan on selling off their ancestral house. Ambika gets to experience strange things happening in the mansion and is told by the locals that she needs to sacrifice her daughter to get rid of the evil to impress goddess Kaali in return. Ambika is in no mood to hear them as she prepares to fight back to save her daughter at any cost.