On the evening of 13 April 1991, Tanner was due to arrive in Oxford by train at 6pm. McLean, 19 years old, went to meet him at the station. Discovering that the train had been delayed, she returned home. At around 7.30pm, Tanner arrived at the house by taxi.[3] The following day was FA Cup semi-finals day in football, and McLean and Tanner, an avid Nottingham Forest fan,[3] planned to spend the day at home. She studied in the front room while he watched the game on television. Afterwards, the couple were seen by neighbours outside the house at around 4.30pm, which was the last time McLean was seen alive.
Later that evening, Tanner strangled Rachel, then forced her head face down and tied a ligature around her neck.[3] In his confession, Tanner told detectives that he spent several hours looking for a hiding place for the body in the house. It took police searchers seventeen days to locate the body hidden in an eight-inch-high gap at the back of a cupboard under the stairs, crammed with household junk. After emptying the cupboard's contents, Tanner had dragged McLean's body, clothed in silky ski pants and a T-shirt, from the adjacent bedroom, along the hall, and into the recess under the floor. He then crawled along under the hallway to hide the body under the floorboards of her bedroom.
Tanner left the house the next day to return to Nottingham, where he was a classics student at the city's University of Nottingham. He was seen by a passenger on the 5pm bus bound for Oxford railway station. As he waited for the 6.30pm train to Nottingham, Tanner penned a love letter to McLean, which he later posted to her Argyle Street address. In the letter, he stated how fortunate it was she had been met by a long-haired man who had offered her a lift home from the station when they were going their separate ways. On 16 April, Tanner telephoned Rachel's home but there was no answer. He tried again the following evening and was answered by Victoria Clare, McLean's 20-year-old housemate. Tanner asked to speak to McLean, but Clare said she knew nothing of her whereabouts. Tanner's letter arrived on 18 April, and Tanner called the house again that evening, asking for McLean.[3]
By 19 April, five days after she was last seen, McLean's friends had begun to wonder where she was. She was due to attend a meeting with her tutor that morning to discuss work for the new term and sit a pre-term exam at St. Hilda's in the afternoon.[3] A phone call to McLean's family in Lancashire confirmed that she had been left in Oxford the previous weekend.