麦兜妈妈Londoner Ronnie embarks on a journey to India when his mother, Suleka, goes missing and mysteriously ends up in a Kolkata hospital. Before Ronnie can unravel the mystery of what brought his mother back to her homeland, Suleka dies in an apparent cult killing. Further deaths point to a series of past murders that stopped 28 years ago when Suleka left India with her infant son. Until now.As the darkness within Ronnie grows and the murders reach their peak, all roads lead to the feared witch of Kolkata's insane asylum.