The Hillside Strangler murders terrorized Los Angeles in the late 1970s. The killers were a pair of sadistic cousins. One confessed. The other was set to stand trial—until L.A. prosecutors flinched.

In 1984, soul legend Marvin Gaye was in the grip of a cocaine habit and living with his father, a hard-drinking Pentecostal preacher with whom he had a lifetime of bad blood. One day, Gaye gave his father a gun and told him it was to protect the house. Some would see an elaborate plan to orchestrate suicide by his father’s hand.

When retired art teacher Joseph Gatto was shot to death inside his Silver Lake home in 2013, the LAPD theorized that a fleeing car burglar might be the killer. The victim’s son, a prominent California legislator, found that story increasingly hard to believe.

Iva Toguri was a Los Angeles native who became trapped in Japan during World War II. When she returned home, the U.S. government put her on trial as a traitor for her wartime broadcasts. Her name became synonymous with a myth, her conviction fueled by lies and political pressure

Aimee Semple McPherson built a religious empire in Los Angeles and became one of the most influential evangelists in America. When she vanished from a California beach and reappeared weeks later with an unbelievable story, the scandal that followed threatened to destroy everything she had built.

On today’s episode, we discuss one of the pivotal events of the 1960s: the assassination of Robert F. Kennedy, a promising presidential candidate at the time of his murder. Though the gunman was caught at the scene, confessed at trial, and even bragged about the shooting, his motives have largely been forgotten. In that collective amnesia, conspiracy theories have flourished.

Orange County’s most prolific mass shooter admits his guilt, but a series of explosive hearings uncovers a longstanding jailhouse snitch operation that taints many other cases. Jailers plead the 5th, the judge makes a startling ruling, and a victim’s husband forms an unlikely friendship with the killer’s crusading defense attorney.

In 2012, the judge presiding over Orange County’s worst mass-shooter case gave a seemingly simple order. He told the Sheriff’s Department to reveal information about a mysterious jailhouse informant. When defense attorney Scott Sanders probed deeper, he announced that he had discovered a wide-ranging and illegal cell-block informant operation—and a conspiracy to cover it up.

In the final episode of this four part series, we’ll talk to historian William J. Mann about his new book on the Dahlia case, which points to the same long-forgotten suspect whose name has been linked to a Zodiac cipher.