In the events of Kat's second stint on the soap, in what was called "the biggest soap story in probably the history of soaps", Kat and Ronnie Branning (Samantha Womack) both give birth on the same day, but Ronnie's baby, James Branning, dies and while Kat is in hospital and her baby, Tommy Moon, is unattended, Ronnie swaps the infants. The storyline received over 6,000 complaints, making it the second most complained about "EastEnders" storyline. Kat's storylines also include suffering a miscarriage, an affair with Derek Branning (Jamie Foreman) which briefly ends her marriage with Alfie, becoming penniless and permanently scarred in a fire and becoming a millionaire. In 2015 Kat's most prominent storyline – the character's rape, is revisited when it is revealed that Kat had given birth to twins and she has a secret son, Zoe's twin brother and this facilitates the characters second exit from the soap. In "Kat & Alfie: Redwater", Kat discovers her son is a murderous Catholic priest, Dermott Dolan (Oisín Stack). Since her reintroduction in 2018, Kat's storylines have focused on the breakdown of her and Alfie's marriage and her separation from her children, a relationship with Kush Kazemi (Davood Ghadami), feuds with both her cousin Stacey Slater (Lacey Turner) and Phil Mitchell (Steve McFadden), which leads to the latter suffering from an injury caused by Stacey, supporting her friend Whitney Dean (Shona McGarty) with her stalker Leo King (Tom Wells) and developing feelings for Phil after sleeping with him.