India, Dec. 24 -- A probe into an armed cab robbery in Rewari unwittingly led investigators to an elaborate, years-long plot allegedly by a PhD scholar to murder a convicted criminal in a bid to avenge an attack on his father, a disabled police officer, more than three decades ago, police said on Tuesday.

The case began in the early hours of December 16, when two men - Devanshu (32) from Ajmer in Rajasthan and Shubham Verma (31) from Azamgarh in Uttar Pradesh - hired a cab from Delhi to Jaipur. At Banipur Chowk on the Delhi-Jaipur Expressway, they allegedly shot the driver, Sanjay Kumar (36), in the leg, took him hostage, and later threw him out on Circular Road before fleeing with the vehicle to Rajasthan.

An FIR was registered at Kaso...