A 14-year-old girl was allegedly hit in the head by a woman while on a train between Colwyn Bay and Rhyl.
British Transport Police is investigating the matter, which was reported to have happened at about 8.20pm on Friday, August 30.
The woman left the train at Rhyl, the force said.
Officers would like to speak to the woman pictured above, as they believe she may have information which could assist their investigation.
A British Transport Police spokesperson said: “Anyone with information is asked to contact British Transport Police by texting 61016 or by calling 0800 40 50 40, quoting reference 2400095981 of August 30.
“Alternatively, you can contact Crimestoppers anonymously on 0800 555 111.”
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