Port Phillip Crime Investigation Unit detectives are appealing for public assistance following a serious assault in St Kilda.
Investigators have been told a 36-year-old female and an unknown male were seated in an outdoor dining area of an Acland St business about 1.10am on 12 November.
It is understood the unknown man was asked to leave by staff due to poor behaviour.
The unknown man has then assaulted a 46-year-old man and the woman, with the woman receiving serious head injuries in the attack requiring surgery.
Investigators have released an image of a man they believe may be able to assist with their enquiries.
He is perceived to be 20-30 years old, with light brown hair and an English accent.
Anyone who witnessed the incident or who recognises the man is urged to contact Crime Stoppers on 1800 333 000 or file a confidential report at www.crimestoppersvic.com.au