Vancouver police investigators are looking for a Good Samaritan who helped a sexual assault victim get home following an alleged attack.

Sgt. Jason Robillard says a woman was walking on Main Street when a man approached her and offered to help her make a phone call just after midnight on Dec. 15.

He says the man then over-powered and allegedly sexually assaulted the woman.

Police believe the suspect was startled and ran off.

He is described as a 30- to 40-year-old Caucasian man with a stocky build and about of 5-foot-6, wearing a black puffy jacket with a red fleece underneath and oversized pants.

Robillard says shortly after the alleged attack a Good Samaritan walked with the woman "a significant distance to ensure she got home safely," and police would like to speak to that person.