A Brighton man was knocked unconscious by a group of men who left him stripped naked and bound with plastic handcuffs.
Police were contacted by the 20-year-old man who was left dazed and confused by the incident, and unable to remember many details.
They are now asking for anyone who noticed a naked man on the streets, possibly in a distressed condition, in the early hours of last Friday to come forward.
The incident is believed to have happened in the Fiveways/Hollingbury area, but police have been unable to glean further information.
Anyone with information is asked to email 101@sussex.pnn.police.uk or phone 101, quoting serial 144 of 06/11. Alternatively they can contact the independent charity Crimestoppers without having to leave their name on 0800 555 111.