A plain-clothes RCMP officer was in the right place at the right time to foil an attempted robbery -- but the would-be victim disappeared while the officer was arresting the bad guys.

Mounties in Burnaby say the incident happened Wednesday afternoon near Metrotown when the woman in her early 20s was surrounded by a group of men.

The officer was alerted by the victim's screams and yelled at her to call 9-1-1 as he chased -- and arrested -- several suspects.

But the woman -- who may not speak English -- was gone by the time the officer returned and police are urging anyone with information about her to give them a call.