Thames Valley Police are appealing for witnesses after a three way collision occured on the Aylesbury Road.
At around 4.35pm, a collision took place between three cars on A418 Aylesbury Road.
The collision involved a red Ford Focus, a red Renault Clio and a grey Range Rover.
Road closures were in place whilst emergency services attended the scene. The road was reopened shortly after 8.40pm.
An occupant of the Clio, a woman in her sixties, sustained serious injuries and was taken to the John Radcliffe Hospital by ambulance where she currently remains.
A man in his thirties and an eight year-old boy, who were both travelling in the Focus, were also taken to the John Radcliffe Hospital.
PC Ashley Jordan, from the Joint Operations Unit for Roads Policing, said: “We would like to speak to anyone who witnessed the collision.
“If you have any information which may assist with the investigation, please call the Thames Valley Police 24-hour enquiry centre on 101, quoting URN 943 of 26 March.
“I’d also like to thank nearby motorists for their patience whilst the road closures and diversions were in place.”
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If you have any information relating to this case, please call 101 quoting reference 'URN 943 of 26 March', or contact Crimestoppers anonymously.