A 45-year-old man is in hospital after being stabbed three times in Swindon's red light district in the early hours.
Police are unsure of the exact location of the attack but believe it happened in the Manchester Road area, or on County Road or Corporation Street.
The victim is believed to have knocked on the doors of a cafe near the Tap and Barrel public house at about 0240 GMT.
A police spokesperson said he remains in a critical condition in the Great Western Hospital.
Det Chief Insp Bob Hamlin said: "The full circumstances surrounding this incident are still unclear, and we have been unable to talk to the victim because of his critical condition in hospital.
"I am looking to the public for help in trying to establish exactly what happened."