Ian Brady was born on 2 January 1938 in the Gorbals area of Glasgow. His birth name was Ian Duncan Stewart. His mother, Margaret Stewart, was a tea room waitress and was unmarried at the time of his birth. The identity of Ian's father is uncertain. His mother claimed that he was a reporter for a Glasgow newspaper who died three months before Ian was born. Because his mother had little support, she eventually placed Ian in the care of a local couple, Mary and John Sloan. They already had four children of their own. Ian took their surname and became known as Ian Sloan. Throughout his childhood, his mother continued to visit him.

When he was nine years old, Ian went on a trip to Loch Lomond with his foster family and found he loved the outdoors. A few months later, the family moved to a council house in Pollok. Some reports suggest that Ian tortured animals during his childhood, although he denied these claims. It was mentioned that he killed a cat at the age of ten and harmed other animals.

Ian's behavior changed while attending Shawlands Academy, which was a school for above-average students. As a teenager, Ian had two run-ins with the juvenile court for housebreaking. He left school at 15 and worked as a tea boy at a Harland and Wolff shipyard in Govan. After nine months, he became a butcher's messenger boy. Ian had a girlfriend named Evelyn Grant, but their relationship ended when he threatened her with a knife after she went to a dance with another boy. After this incident, he faced multiple charges in court and was placed on probation, which required him to live with his mother.

By this time, Ian's mother had moved to Manchester and married an Irish fruit merchant named Patrick Brady. Patrick helped Ian get a job as a fruit porter at Smithfield Market, and Ian began using his stepfather's last name. Within a year of moving to Manchester, Ian was caught trying to steal lead seals from the market and spent three months in Strangeways Prison. Since he was still under 18, he was sent to a borstal for two years for "training." He was transferred to different institutions, including Latchmere House in London and a tougher one in Hull.

After being released in November 1957, Ian returned to Manchester. He took various laboring jobs but was unhappy with them. Wanting to improve himself, he borrowed bookkeeping manuals from the library and spent many hours studying them. In January 1959, Ian applied for and got a clerical job at Millwards Merchandising, a chemical distribution company in Gorton. His coworkers described him as quiet, punctual, and short-tempered. He enjoyed reading books, including German language guides and works about Nazi Germany, while also riding a motorcycle to explore the Pennines.

On July 12, 1963, Ian Brady and Myra Hindley committed their first murder. They lured 16-year-old Pauline Reade, offering her a lift on her way to a dance. They took her to Saddleworth Moor under the pretense of searching for a lost glove. Once there, Brady assaulted her and killed her. Pauline's body was buried on the moor.

The second murder occurred on November 23, 1963. They offered 12-year-old John Kilbride a ride home from a market, but instead took him to the same moor. Brady attacked him in a similar manner to Pauline. After killing John, they buried his body on the same moor.

On June 16, 1964, they abducted another child, 12-year-old Keith Bennett. Hindley pretended to ask him for help loading boxes into her van. Once they reached the moor, Brady took Bennett away, and he did not return. Brady later told Hindley that he had killed Keith and buried him in a shallow grave.

Their fourth victim was 10-year-old Lesley Ann Downey, whom they kidnapped from a funfair on December 26, 1964. Once in their home, she was raped and murdered, and Brady recorded parts of the attack. They took her body to Saddleworth Moor and buried it alongside the others.

The final victim was 17-year-old Edward Evans, whom Brady and Hindley targeted on October 6, 1965. Brady met him at a railway station and took him back to their house. After a violent struggle, Brady killed Evans with a hatchet and later made an attempt to hide his body in the home.

After the murder of Evans, David Smith, who was Hindley’s brother-in-law, witnessed the crime. The following day, he reported what he had seen to police, leading to the arrest of both Brady and Hindley. Their investigation unveiled evidence connecting them to the earlier murders, ultimately leading to their conviction.