Officers from British Transport Police are appealing for witnesses following a fight on board a train between Edinburgh Waverley and Glasgow Queen Street.
The incident happened on Saturday 13 January on the 8.22pm service, when passengers reported that a man and woman were fighting during the journey.
Police officers met the service and the details of the man and woman were taken and they were allowed to go on their way.
Officers are now keen to identify any witnesses who were on board this train and saw what happened.
Eyewitnesses are asked to contact police by sending a texting 61016 or by calling 0800 40 50 40 and quote reference 573 of 13/01/2018. Alternatively, contact Crimestoppers anonymously on 0800 555 111.