Officers were alerted to the collision on the A168 at around 10pm on Wednesday 3 April 2019.
A red Vauxhall Astra, which was travelling north and a silver Volkswagen Polo, travelling south, had collided just after the flyover near the Bridge Hotel in Walshford.
The driver of the Astra, a man in his twenties sustained serious, potentially life changing injuries.
The driver of the Volkswagen, a woman in her thirties also sustained serious injuries, along with a male front-seat passenger, and a child with a suspected broken leg, who was travelling as a rear seat passenger.
Very sadly a 68-year-old woman, who was also travelling as a rear seat passenger in the Volkswagen, died at the scene.
The road was closed to allow emergency services to attend and remained closed to allow the Forensic Collision Investigation Unit to carry out a thorough investigation of the scene.
Officers are now appealing for witnesses to contact them, so they can establish the full circumstances around the incident.
They are particularly interested to speak to anyone who was travelling along this stretch of road immediately prior to 10pm, anyone who witnessed the collision itself, or anyone who saw either car in the moments prior to the collision. Also, anyone who may of captured dash cam footage is urged to get in touch.
Please contact 101, select option 2 and ask to speak to either Temporary Detective Sergeant 1658 Kirsten Aldridge or Traffic Constable 1068 Adam Elliott.
Alternatively you can email Kirsten.Aldridge@northyorkshire.pnn.police.uk or Adam.Elliott@northyorkshire.pnn.police.uk – please quote reference 12190060095.