|After Kitty returns to NYC to warn Holmes that those that prosecuted a case in London involving Eli Kotite are all dying, Watson notices that Kitty is evasive when asked questions about her life. Leaving the investigation several times without explanation, Watson waits until Kitty leaves a brownstone she's staying at. Breaking in, she's attacked by a large woman who she struggles with, smashing a window. The woman pins Watson against a wall and chokes her until Kitty bursts in and tells her to stop. Introducing the woman as Margaret, much to Kitty's dismay, Margaret says she's a nanny and is taking care of Kitty's baby. In the kitchen, Kitty shows Watson her son, Archie. Explaining that she and Archie's dad aren't together, but he is very supportive, she kept Archie a secret as she felt that they won't let her participate in the case if they knew she was a mother. Later, she introduces her nanny Margaret and Archie to Holmes, who is surprised, but is interrupted by a call from Kotite. ("Wrong Side of the Road")|
|Having been asked to leave the house they were staying at due to the damage caused by the fight between her and Watson; Margaret, Archie and Kitty move to the Brownstone. Margaret cares for Archie while Kitty continues investigating with Holmes and Watson. Margaret finds a dollhouse and dolls in the guest room which she brings downstairs for Archie to play with until she notices that the dolls are dead. Kitty explains that Holmes uses the dollhouse for crime scene training. She then uses a gadget to amuse Archie until Watson tells her there's a good chance the gadget is a Victorian sex toy. Later, at St. Marks church, Archie is christened with Holmes and Watson being made the godparents. ("Fidelity")|
|In May 2019 at 221A Baker St., as Kitty discusses Watson's unhappiness with living in London, Archie plays with blocks. Later, as Kitty tries to get information from Ruby Carville, Holmes sits on a bench with Archie, eating an ice cream cone. ("The Further Adventures")
- Kitty has agreed to take Clyde once Holmes and Watson die. Archie will take him after Kitty dies. ("The Adventures of Ersatz Sobekneferu")
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