A watchdog is looking into a case where a man was arrested on suspicion of attempted rape after police attended a Berkshire home twice in the same day.
Officers had earlier spent 30 minutes at the house in Slough on Friday evening dealing with an "incident".
Two hours later a man aged 22 was hit by a car near the house, and police discovered a 53-year-old woman at the house had suffered severe injuries.
The man was arrested and the police watchdog informed.
The Independent Police Complaints Commission said it would look into the details of the case and decide whether it will investigate.
The woman was taken to hospital with serious injuries.
The man, who has been transferred to a psychiatric secure unit, was also arrested on suspicion of causing grievous bodily harm.