Obsessed with Nazi atrocities and crime, Ian Brady began his criminal career at 13, when he was placed on probation for theft and attempted housebreaking. After a stint in prison, Brady managed to get a job as a stock clerk in Manchester, England, where he met typist Myra Hindley.

Hindley, the product of a working class Manchester family, became infatuated with the dark and brooding Brady. Fascinated by his unconventional interests and tendency toward sadism, Hindley totally devoted herself to Brady, even bleaching her dark hair to more closely adhere to the Nazi conception of physical beauty.

In July 1963, Brady and Hindley committed the first of the infamous Moors Murders when they killed 16-year-old Pauline Reade. The murders of 12-year-old John Kilbride, 12 year-old Keith Bennett, and 10-year-old Lesley Ann Downey would follow soon after.

As documented in Emlyn Williams’ “Beyond Belief: A Chronicle of Murder and its Detection,” Brady and Hindley’s murder spree would end when Hindley’s brother-in-law, David Smith, whom Brady was grooming to be an accomplice, reported witnessing Brady’s murder of 17-year-old Edward Evans to the police. Authorities would later discover recordings and photographs that Hindley and Brady made of their killing of Downey. The bodies of Downey and Kilbride were discovered buried on Saddleworth Moor in 1965. Reade’s remains were located there in 1987, and Bennett’s body has never been found.

Although Delfina and Maria de Jesús González (sometimes spelled Gonzáles) may not have the name recognition of Charles Manson, the Zodiac Killer, or the Boston Strangler, they were two of the most active killers of the 20th century. An estimated body count of 90 earned them the dubious distinction of the Guinness World Record for the most prolific murder partnership.

As detailed by Murderpedia, the sisters — known as Las Poquianchis — grew up in poverty under the thumb of their volatile and abusive father in El Salto de Juanacatlan, Jalisco, Mexico. As adults, Delfina and Maria de Jesús struggled to survive and turned to sex work to make ends meet. Soon, they were operating a chain of successful bordellos under the noses of well-greased police and officials.

To keep their business well-staffed, the sisters roamed the countryside offering poor girls and women lucrative jobs as maids or waitresses. Often, they would simply kidnap girls with the help of Delfina’s lover, Army Capt. Hermengildo Zuniga. Once in the sisters’ clutches, the young women were forced into sex work. The penalty for pregnancy, sickness, or attempted escape was death, often by torture or starvation.

Las Poquianchis’ reign of terror ended in January 1964, when Catalina Ortega escaped the sisters’ clutches and reported them to the police in Guanajuato. The González sisters were sentenced to 40 years in prison. Elder sister Delfina died in prison, but Maria de Jesús completed her sentence and then dropped out of public view.

As featured in “Biography,” Richard Benjamin Speck was born in Kirkwood, Illinois, on December 6, 1941. By the time he was 15, Speck had developed an insatiable taste for alcohol. Soon, he dropped out of high school and embarked on a life marked by misogyny and violence.

In 1965, he was sent to Texas State Penitentiary for assaulting a woman in Dallas. Back on the streets just months after the attack, Speck moved to Monmouth, Illinois, where he attacked a 65-year-old woman and beat barmaid Mary Pierce to death. Feeling the heat from the police, Speck left for Chicago, where he found work on a ship before being fired for pulling a knife on a superior.

On the night of July 13, 1966, he entered a South Chicago townhouse occupied by student nurses. Slipping through an open window, Speck bound, beat, strangled, and stabbed eight women. Only Corazon Amurao, who hid under a bed, would survive to identify the killer.

Days after the rampage, Speck attempted suicide. He was rushed to a hospital, and, according to “Born to Raise Hell: The Untold Story of Richard Speck,” a doctor recognized Speck’s “Born to Raise Hell” tattoo from police reports. Speck was sentenced to death in 1967, but a 1972 Supreme Court moratorium on the death penalty saved him from the electric chair. Speck suffered a heart attack at Stateville Correctional Center and died in hospital on December 5, 1991. Speck was suspected of murdering seven more women in Indiana and Michigan.

As documented in Max Haines’ “True Crime Stories, Book II,” Provincetown, Massachusetts, on the northern end of Cape Cod, became something of a counterculture haven in the late 1960s. Hundreds of hippies flocked to the New England resort town. However, a monster lurked in their midst.

By 1968, Tony Costa was growing marijuana on a remote plot of land hidden behind a cemetery in nearby Truro. Costa’s easy access to weed made him popular with Provincetown’s youth, and he relished the attention — especially when it came from young women.

In January 1969, Costa was suspected in the disappearance of Pat Walsh and Mary Anne Wysocki. An initial sweep of the Truro woods failed to locate Walsh and Wysocki, but the search turned up the dismembered remains of a different woman. With the help of one of Costa’s acquaintances, the police were able to locate Costa’s drug garden. Nearby, they found the mutilated remains of Wysocki, Walsh, and another victim. Convicted only in the slayings of Wysocki and Walsh, Costa was given life in prison.

Author Kurt Vonnegut became fascinated by Costa when he learned that his daughter had met the killer and declined his invitation to visit his marijuana patch. Writing about the murders in a feature for Life, Vonnegut compared Costa to Jack the Ripper. Vonnegut maintained a brief correspondence with Costa, in which the killer asserted his innocence. Costa committed suicide in prison in 1974.

As documented by Biography, the first widely attributed murders of the serial killer who would become known as the Zodiac were on December 20, 1968, when he shot David Faraday and Betty Lou Jensen to death on a secluded road near Vallejo, California. Six months later, another couple met a similar fate.

In August 1969, the killer wrote letters to the San Francisco Examiner and the Vallejo Times-Herald detailing the murders. Each message contained a complex cipher with possible clues about the murderer. More taunting letters would arrive containing new codes — one declaring that the victims would become his slaves in the afterlife.

On September 27, 1969, the killer struck again, this time targeting Cecelia Shepard and Bryan Hartnell as they relaxed on the shores of Lake Berryessa in Napa County. After binding the couple, he repeatedly stabbed them. The killer then left a message and his mark on the door of Hartnell’s car. Shepherd died from her wounds, but Hartnell survived. Two weeks later, the Zodiac killed a San Francisco taxi driver.

Despite surviving witnesses, fingerprint evidence, decoded ciphers (the last of which was solved in 2020), and numerous suspects, the identity of the Zodiac Killer remains unknown as of 2021.