A man suffered serious head injuries in an attack in Crawley.
Four people have been arrested after a 53-year-old man, of no fixed address, suffered a deep cut to his head and extensive facial injuries.
He is being treated at the East Sussex Hospital in Redhill.
Detective Inspector Mark Cullimore said: "We are investigating an attack involving people known to each other. The nasty assault happened on Tuesday night, at about 9.45pm, in and outside a house in Shaws Road, Northgate.
"I am appealing to anyone who witnessed what happened to call police on 101 or email firstname.lastname@example.org or the independent charity Crimestoppers anonymously on 0800 555 111."
Four people, a woman aged 47 and men aged 27, 16 and 15, have been arrested for assault occasioning grievous bodily harm and are in custody.