The story started its life in the mind of Nobel Prize winning author John Steinbeck, who considered his 1952 East of Eden novel his magnum opus. While there have been multiple adaptations over the years, the latest from writer and co-showrunner Zoe Kazan remains faithful to much of the original story while offering a more modern interpretation of what made Cathy the way she is.

In Steinbeck’s novel, Cathy is introduced as an almost inherently evil figure, with the narrator even questioning whether she was born a “monster”. Kazan’s adaptation doesn’t excuse the horrific things she goes on to do, but instead re-examines moments from her childhood that Steinbeck originally used as evidence of her wickedness.

That includes the suggestion Cathy was sexually abused as a child, with the series reinterpreting her fascination with Alice in Wonderland and desire to shrink herself – details taken from Steinbeck’s novel – as signs of childhood trauma and dissociation.

While these changes add more context to Cathy’s actions, the sprawling story remains intact. That includes her marriage to Adam Trask (Christopher Abbott), and the birth of their twin sons, Cal (Joseph Zada) and Aron (Joe Anders).

She never wanted to have those children, and so she cold-bloodedly shoots her husband and abandons them all (Adam survives, but pines after her for many years after).

Cathy eventually reinvents herself as Kate and takes control of a brothel, while Adam raises their sons, who believe she’s dead. When they move nearby, Cal discovers the truth about his mother and repeatedly seeks her out at the brothel, while Aron remains completely unaware that she’s still alive.

But when the two boys get into an argument, Cal angrily takes his brother to see Cathy, leading to a gut-wrenching reunion. Aron storms out and joins the US army to fight in the First World War, where he tragically dies.

Just before the Trasks find out this devastating bit of news, Cathy – who has been slowly losing her sanity – takes her own life. She leaves behind her will, and despite having had the most interaction with Cal, she names Aron the beneficiary of her fortune.

So, why did Cathy leave everything to Aron?

It’s an answer that isn’t explicitly given in the East of Eden book, but one of the most convincing readings is that Aron’s visit provokes something in Cathy that she’s never experienced before: a genuine maternal feeling and the recognition of something good that she lacks within her.

What’s telling is that in the book – and in the Netflix series – Cathy’s mind had been deteriorating, but it’s only after meeting Aron for the first time since abandoning her boys that she makes the decision to kill herself.

As she’s recalling both Aron and Cal’s faces the night prior, she thinks, “They had something she lacked, and she didn’t know what it was. Once she knew this, she was ready; and once ready, she knew she had been ready for a long time – perhaps all of her life.”

Up until this point, Cathy has always been sure that she understands people better than they understand themselves, believing that underneath it all, everyone is capable of the same cruelty and corruption as her.

But as Steinbeck in the Schools writes in her character summary, “The meetings, along with growing paranoia about the evil deeds of her past resurfacing, cause Kate to question herself.

“Having always been self-assured in her isolation from what she saw as great depravity in other people, she begins to wonder if perhaps it is she who is different. Particularly, her meeting with Aron, who is brought to her out of revenge by his angry and rejected brother, brings this fact into relief.”

In that sense, leaving Aron her fortune could be read as Cathy’s final attempt to make amends for abandoning him. But as is the case with any big decision in life, there are bound to be multiple motivations.

Steinbeck deliberately makes her motive ambiguous, something Kazan spoke about in a conversation with The Wrap. When asked about the inheritance, she replied, “I also ask that question, and I don’t know. That is a mystery to me, and I love that about it. It’s not just one thing.”

There could be another reason Cathy chooses Aron over Cal

One interpretation extends the theory, suggesting that Cathy sees a vulnerability in Aron but also recognises herself in Cal – and as a final act, she gives Aron the money as she knows Cal can fend for himself.

A reader shared this idea on Reddit after reading East of Eden, writing, “I felt Cathy with her last act, showed her only notion of… motherhood? She gave her fortune to Aron. Maybe she saw in him the weaker of her sons. The one who couldn’t make a small fortune for the fun of it (much like Adam couldn’t).

“It was an act of love. She saw him for who he was. Everyone else saw him and loved him, was so impressed by him. She saw through it. Ultimately knowing he would be the one to need her help.” They added that she knew Cal enough to know he wouldn’t need the money.

A perfect example of this in the story is when Cal decides he wants to make his father’s fortune back from the failed business, and he does so quite easily through his investment in beans during the war.

From this perspective, leaving Aron everything isn’t necessarily about loving him more than Cal. Cathy may simply understand that Cal possesses the same ability to survive that she does, while Aron doesn’t – and her fortune is the only protection she can leave him.

Of course, the cruel irony in this isn’t just that Aron dies before inheriting his mother’s fortune. It’s also that the money itself came from the brothel and through Cathy exploiting the people around her.

Adam refuses to accept Cal’s bean money knowing he’s been sending young men to war, and Aron – a character who is arguably even more obsessed with goodness and purity – would simply not have been capable of accepting the tainted wealth.

The irony isn’t lost on Lee (Hoon Lee) in the novel. After learning about Cathy’s will, he “laughed to himself” imagining “Aron, whose purity was a little on the self-indulgent side, living all his life on the profits from a whorehouse.”

He then wonders: “Was this some kind of joke or did things balance so that if one went too far in one direction an automatic slide moved on the scale and the balance was reestablished?”

This has led to an altogether darker interpretation of Cathy’s will. Rather than viewing the inheritance as a form of maternal love and making amends, some readers have questioned whether Cathy is effectively forcing herself upon Aron as a final act of spite.

He is horrified by what his mother represents, and so making him the sole heir to the wealth she’s accumulated through murder, exploitation and cruelty certainly would be one way to hurt him before her death.

As one Redditor theorised, “Her willing her money to Aron is nothing more than a calculated move to spite him, as the personal embodiment of purity and goodness within the story.”

It’s worth noting that this particular reading is far more associated with the novel than the Netflix series, which, as said, gives Cathy’s motivations more context as she reflects on the trauma of her childhood when she dies.

While speaking to Netflix’s Tudum about the ending, Pugh herself described Cathy’s final vision of her younger self as returning to “the beginning of it all”, explaining that the abuse she suffered created the “knock-on effect” that influenced the decisions she made throughout the rest of her life.