Charlie, a taxicab driver who is widowed from Viv Slater, arrives in Walford with Viv's mother Mo Harris and Charlie's five daughters: Lynne Slater, Kat Slater, Little Mo Slater, and Zoe Slater, plus Lynne's boyfriend Garry Hobbs. It soon emerges that Kat is actually Zoe's mother and that it has been kept a family secret until Zoe finds out. Demanding to know the identity of her birth father, Zoe and Charlie are stunned to discover that it was Charlie's brother Harry Slater, who raped Kat when she was a teenager. Little Mo, now married to Billy Mitchell, is raped by Graham Foster. When Charlie finds out, he attacks Graham after locking him in his taxi. Charlie is arrested and remanded in custody for grievous bodily harm, to which he pleads guilty but the family has to pay Graham £10,000 compensation. Charlie's cab license is revoked, but is later restored. Lynne, now married to Garry, leaves Walford after her baby, Vivienne, is stillborn. Charlie's great-niece Stacey Slater moves in, and Charlie becomes a father figure to her, helping her curb her rebellious and wayward attitude. At the same time, he comforts Zoe after she has an abortion. Zoe eventually leaves, soon followed by Kat who is now married to Alfie Moon. However, Stacey's mother Jean Slater moves in with the family.
Charlie puts an advertisement in a lonely hearts column and becomes a member of an internet dating website, meeting and falling for Brenda Boyle, a Salvation Army member from Clacton. However, their romance begins to fizzle out. After not seeing each other for several weeks, Brenda ends the relationship, telling Charlie that she and her brother are moving to Madeira. Not wishing to end the relationship, Charlie gets approval from Stacey and Mo to go with her. He returns not long after with a Russian woman named Orlenda. Mo is suspicious of her and follows her around. On seeing her with another man, Mo takes a photo to show Charlie. Charlie confronts Orlenda who admits that she was using Charlie for his money and he asks her to leave. When Stacey stops taking medication for her bipolar disorder, Charlie insists that she has to start again as she almost lost her baby Lily. Charlie asks Dot Branning to speak to Stacey as he believes that Lily's father is Stacey's deceased husband Bradley, Dot's step-grandson. Dot then reveals that Lily is not Bradley's. Charlie asks Stacey why she has not told the truth and begs her to take her pills, trying to force one into her mouth. Stacey says she has already taken them and Charlie apologises, then walks out of the house in tears. He spends the night at Patrick Trueman's house, and invites Patrick and Jim Branning for drinks. Later, Sam Mitchell asks Charlie to take her to the hospital because she is worried her baby Richard is unwell, however after driving part way, Charlie tells her the symptoms are normal. As he turns around, he reverses into some boxes in front of a van, and is then stopped by a police officer. The next day, Mo opens a letter for Charlie and learns was caught driving over the limit. They argue as he could lose his driving licence, and Charlie later apologises to Stacey for forcing her to take her pills.
Charlie is shocked when his daughter Kat returns to Albert Square. Kat is trying to avoid some thugs to whom she owes money. They catch up with her at Charlie's house, and Kat tries to escape. In the commotion, Charlie reminds Kat that she hasn't even asked about his life or anyone else's in Walford. Kat's estranged husband Alfie then arrives and chases the thugs away. However, Charlie is then dismayed to learn that Kat is pregnant, and Alfie is not the father. Alfie and Kat reopen The Queen Vic as landlords and give Charlie a job there as a potman. Kat gives birth to Tommy, on the same day Ronnie Branning gives birth to her son, James. Kat is rushed to hospital, leaving Tommy in Charlie's care, but he joins the New Year's Eve party instead. James dies of cot death, so Ronnie secretly swaps him with a perfectly healthy Tommy. Alfie and the rest of the family then discover the dead baby, believing it to be Tommy. Charlie admits to Kat that the baby was left alone as he was drinking, so Kat blames him for the baby's death. Charlie tries to make things right, but eventually realises it is best for him to leave. Mo begs him to stay but he refuses. Mo tells Kat and Alfie, and when Alfie says fathers have feelings too, they run to the tube station. Kat forgives Charlie and he leaves to stay with Lynne. When Kat and Alfie receive Tommy back, Charlie visits Kat and helps her bond with her son. Kat asks Charlie to return to Walford, but he refuses as he is in a relationship with a younger woman named Eileen, and they are getting married. Soon after, he returns to Lynne's. Off screen, Charlie suffers a stroke. Kat, Alfie, Tommy and Shenice Quinn go to visit him in hospital and stay with him for a while. Soon after Alfie returns with Shenice and reveals Kat and Tommy are staying with Charlie until he recovers. Kat later returns to Walford with Tommy. Charlie visits Kat and Alfie for Christmas to celebrate their last days in The Queen Vic, and is delighted to learn that Kat is pregnant again.
Charlie returns following the birth of Stacey's son Arthur Fowler. Kat then learns that she had given birth to a boy along with Zoe. Charlie admits to Kat that he knew about Stacey's father, Brian's, other family and that he did nothing to stop him. When an angry Kat demands the truth from Mo about her son, Charlie suffers a heart attack. Charlie manages to tell Kat that he loves her, before going into cardiac arrest. The paramedics arrive minutes later, but are unable to save Charlie and he is pronounced dead. Alone, Kat says her final goodbyes to her father before kissing him goodnight on the forehead. Shortly afterwards, Stacey runs away from Walford, however, she has an hallucination of Charlie (a symptom of her postpartum psychosis), in the form of a taxi driver who convinces her to return home.