Warning! This article contains spoilers for Cross season 1.

Warning! This article contains mentions of murder.

A crucial story development in Cross season 1 reveals what happened to Ed Ramsey’s sister and how her fate eventually influenced the killer’s future actions. Based on James Patterson’s Alex Cross books, Cross season 1 primarily follows a linear narrative where the titular detective character sets out to catch two criminals. While one is responsible for his wife’s murder, the other is a serial killer with a twisted mission to kill twelve individuals.

The latter turns out to be an influential man, Ed Ramsey, whose obsession with killing can be traced back to his childhood. To learn more about his past, Alex Cross’s best friend, John Sampson, also visits his mother. This is when he learns the truth about what happened to Ed Ramsey’s sister and how her fate eventually played a crucial role in turning him into a vicious serial killer.

Ed Ramsey Killed His Sister Via Carbon Monoxide Poisoning So He Could Be An Only Child

He Murdered His Sister Out Of Jealousy

After John Sampson visits Ed Ramsey’s mother in Cross season 1, he learns the truth about his past and the events that gradually turned him into a deranged serial killer. Ed Ramsey’s story in Cross season 1 reveals that he was once his single mother’s only child, which made him the center of all attention. However, a few years later, his sister was born, which divided his mother’s affection between her two children. Over time, he grew increasingly jealous of his sister and even told his mother he wanted to be her only child.

Soon after Ramsey grew resentful towards his younger sister, she passed away from accidental carbon monoxide poisoning. Since the death was ruled accidental, no one was blamed for it. However, the truth was that Ramsey had secretly poisoned her, believing that it would help him get back his mother’s undivided attention. Although Ramsey never got caught for killing his younger sister, this early incident from his childhood revealed his violent tendencies. But, to his dismay, even though he executed his sinister plan without facing repercussions, Ramsey could not get what he wanted.

Ramsey’s Sinister Plan With His Family Completely Backfired

He Did Not Get The Affection He Craved From His Mother

Ed Ramsey killed his sister because he believed that it would help get more attention from his mother. However, his plan backfired when his mother grew even more emotionally distant from him after his sister’s demise. Overwhelmed by her grief for her daughter, Ramsey’s mother could not help but build many walls between herself and her son.

As Alex Cross later discovers, Ramsey could not handle the growing distance between him and his mother. Therefore, he even started killing birds in the neighborhood. As his violent tendencies got worse over time, he gradually started idolizing famous serial killers and turning into Cross‘ central “Fanboy Killer.” Although Ramsey’s mother’s dementia prevents her from remembering many details of her past, she is able to recall how Ramsey’s behavior gradually became worse when John Sampson gives her some strong prompts to jog her memory in Cross season 1.