British Transport Police are hunting a man who committed two acts of indecency on a train between Greenfaulds and Edinburgh Waverley.
The incident happened at 6.35pm on Friday, November 29 - when the man was seen indecently touching himself - then exposing himself to a female passenger, before disembarking at Polmont
The suspect is described as white, five foot 10 inches tall and in his late 20s. He had short dirty blonde hair and a beard which was blonde or ginger in colour.
He was wearing a green hooded top with white writing on the right sleeves. He was also wearing green cargo-style trousers and was carrying a grey holdall.
Anyone who knows the man is asked to contact BTP by texting 61016 or by calling 0800 40 50 40 - quoting reference number 591.