The investigators zeroed in on Vidyasagar as the main culprit following sustained questioning of the four persons detained in connection with the murders of Hema Upadhyaya (43) and her lawyer Harish Bhambhani (65).
"The questioning of the four detainees, including the one held today in Varanasi, led to the information that the murder took place at the behest of a person called Vidyasagar Rajbhar," a senior police officer, who is part of the probe team, said.
On Saturday night, the day they were believed to have been killed, it was Vidyasagar who had called Hema on her mobile at 7.30 pm, the officer said.
Vidyasagar's arrest will help the police join the missing dots, he added.
Shivkumar Rajbhar alias Sadhu, who was today detained by the Uttar Pradesh Special Task Force in Varanasi following a request by the Mumbai police, went public with the claim that the two were killed under instructions from Vidyasagar.