Police want to trace a woman over an attack on another woman at Doncaster railway station.
They believe she may hold vital information about an incident at 10.30pm on Saturday, December 9 when violence flared on the platform.
British Transport Police said a woman in her 30s boarded a train at Rotherham, heading towards Doncaster, and a row broke out involving her and a group of other women.
It spilled onto the platform and the victim was then punched in her face.
She suffered a black eye and bruising to her cheek.
Anyone with information should call British Transport Police by sending a text to 61016 or by calling 0800 40 50 40.