A 15-year-old suffered serious head injuries after being hit by a car on the city's Bransholme estate.
The cyclist who was riding a red bicycle collided with the blue Ford Fiesta around 10pm on Monday.
The accident, which happened on Wawne Road with the junction of Barnstaple Road, left the youngster with serious injuries to his head and minor back injuries.
The driver of the car suffered minor injuries to his hands.
No arrests have been made.
Police are asking witnesses to come forward.
They also want to hear from a man who is thought could have taken some of the teenager’s clothing and a blanket before emergency services arrived.
The only description they have of him was that he was wearing a vest.