The accused, Irshad Siddiqui (28), had allegedly sexually assaulted his wife's younger sister on Sunday, they said.
According to a police official, the accused and his wife, who reside in Rajkot in Gujarat, had come to the latter's maternal home in Bandra to attend her mother's funeral. Her mother had died in a road accident a few days back.
"On Sunday afternoon, the accused raped his wife's sister when she went to sleep. Following the incident, the victim went to her neighbours and narrated her ordeal to them. They approached the police and lodged a complaint against Siddiqui," he said.
Three police teams were formed to probe the matter and sent to various places, including Rajkot, to nab the accused, the official said.
Siddiqui has been booked under section 376 (rape), 323 (punishment for voluntarily causing hurt), 354 (assault or criminal force to woman with intent to outrage her modesty) and other relevant sections of IPC.
He has also been booked under the Protection of Children from Sexual Offences (POCSO) Act, the official said.