Paappi Devataa is a story about Rahim Khan, who lives a poor life-style with his mother and adopted sister, Reshma. Rahim, a devoted Muslim, works as a truck driver for a company owned by Niranjan Das and his assistant, Ratan Seth.
One day, Rahim discovers drugs in his truck and confronts his superiors about it. This leads to an argument between Niranjan and Ratan, revealing that Ratan has been embezzling company money for his personal use.
In a twisted turn of events, Ratan sets up a situation where Niranjan is forced to sexually molest Reshma, Rahim's sister. Rahim reacts by shooting and killing Niranjan.
Ratan manipulates Rahim into continuing to work for him by delivering drugs, this time as a taxi driver. The police, led by Deputy Commissioner of Police, Ram Kumar Singh, get involved in the investigation of Niranjan's death.
Ram befriends Rahim and they start sharing the same roof and taxi driving profession. However, when the time comes to arrest Rahim, Ram must put aside their friendship and emotions.