"Kat and Alfie: Redwater" follows Kat and her husband Alfie as they arrive in the fictional Irish village of Redwater to "search for answers to some very big questions" and put their past behind them. Treadwell-Collins confirmed that "the discovery that Kat has a secret son will [...] ultimately lead to the Moons realising that the answers to so many questions lie across the sea in Ireland." Director Jesper W. Nielsen said the series is "About how one woman's search for a lost child opens Pandora's box; revealing the terrible lies and secrets in the little village of Redwater". Writer Matthew Graham said, "Kathleen Moon is an unwitting bomb in "Redwater" and creating the debris from her explosive arrival is what drew me to this project." He also said: "Everything does comes out of the fact she doesn't think much of herself. So, her humour and her in-your-face qualities all come out of a place of insecurity. She doesn't think she's good enough. That's what I use when I'm writing Kat."