Police are appealing for witnesses after woman noticed a man staring at her while masturbating on a Stirling train.
The incident took place between 11.30am and 12.20pm on a Larbert to Stirling train on February 8.
The service was between Edinburgh Waverley and Dunblane at the time.
The woman challenged the man before leaving the carriage.
The man is described as white, of slim build, and between 35 and 40 years old.
British Transport Police say he had short fair hair and was wearing dark-coloured round glasses.
He was also wearing a blue jacket with a red puffer-style jacket, a checked shirt, and blue jeans.
He was carrying a black and grey rucksack with a white ‘Nike’ logo.
A spokesperson for the force said: “Officers are appealing for anyone who may have witnessed the incident to get in touch with them to assist the investigation.
“Anyone with information is asked to contact BTP by texting 61016 or calling 0800 40 50 40 quoting reference 2400016948 of 08/02/24.
“Alternatively you can call Crimestoppers anonymously on 0800 555 111.”