Detectives are looking for a Good Samartian who helped a young woman in Cardiff Bay over the weekend.
Two men have been arrested following a disturbance in the Mermaid Quay area on Saturday night.
It's understood the witness stopped to help a 19 year-old woman who appeared to be intoxicated and vulberable in the company of two men at around 9.45pm.
South Wales Police have stressed she's done nothing wrong but they believe she may have important information relating to an ongoing investigation.
The Good Samartian is described as in her mid-twenties, brunette and wearing a fur coat.
Anyone who witnessed the incident or may have any further information should contact South Wales Police on 101 or via the live web chat, quoting reference no. 2600023189.

Candidates confirmed for by-elections
Drug dealing gang jailed for 45 years
Council drops school budget warnings
Burger stand owner fined for hygiene breaches
Deputy First Minister pledges cleaner rivers
Two missing people found in overnight searches
Unsolved: fresh bid to find taxi driver's killer
Calls for Old Harbour reserve turned down
Barry man charged with assaulting police officers
Talks to be held on Cardiff Rugby sale
Barry Arts Festival returns with Waldo play
No decision yet on Barry wood plant
Plaid wins St Athan by-election
Council to relaunch street cleaning service
Petition supporting Tree Preservation Order reaches 1,000 signatures
Le Tour comes to Cardiff
Trampoline park owner avoids jail