Hull Black is a seemingly normal child, at least in the Holmes family. She is the most normal child.
Just five days after Mycroft's 25th birthday, he finally got his birthday gift back from MI6 - a 7-year-old little girl.
From then on, Mycroft, who wanted to be a father, had another person to worry about, the Holmes family's goldfish.
In this regard, Mycroft said that Hel is a little mermaid, and she is much easier to control than her restless younger siblings.
Little did they know, the rebellious period of the goldfish would come with great vigor, and even more so of the mermaid of the Holmes family!
Mission: Family is a safe haven