A man has been arrested on suspicion of murder after a woman was found dead at a flat in West Sussex.
Police found the woman at the flat in Highams Hill, Gossops Green, Crawley, just after 22:30 BST on Friday.
According to a neighbour, a "very upset" man had been frantically searching for her after she failed to turn up to her 28th birthday party.
A 47-year-old man is being held on suspicion of murder and remains in custody.
Det Ch Insp Emma Heater said the man and woman were known to each other.
He was found in the property with minor injuries and was checked by paramedics before he was arrested, Sussex Police said.
Det Ch Insp Heater said: "I can't formally identify the woman but I do have family liaison officers with family members of whom we believe the victim to be.
"The cause of death is not known at this time. However a post-mortem will be conducted tomorrow."
Friends raised the alarm after the woman failed to turn up to pre-arranged plans, police said.
Aaron Harvey, 24, who lives nearby, described how police "flooded" into Highams Hill.
He said a man approached him looking for a blonde 28-year-old woman.
He said: "He seemed very upset and worried.... I felt sorry for him, he was panicking... he said no-one had heard from her for about 10 hours.
"He said it was her birthday and she had booked a hotel in London to celebrate with friends but never turned up."
He said the man was making phone calls and then police turned up.
"First there was one car, then suddenly loads more flooded into the street, and vans and paramedics," he said.
Shortly afterwards, he said he saw a different man being pushed out of the block of flats in a wheelchair "covered in blood".
He added: "He was taken over to the ambulance to be treated. We have never seen him before so we don't think he lives here."
Police urged anyone with information to get in touch.