| Yvette Ellison |
|Family|| Rebecca Ellison (twin)|
Charles Ellison (father)
Casey McManus (half sibling)
Anna Webster (half sibling)
|Behind the scenes|
|Appearances||"While You Were Sleeping"|
|Portrayed by||Amy Landon|
- "There were only two pretermitted heirs, Ms Ellison. Yvette killed the second one yesterday. So tell me: Why was she still in a coma today? Why did not she miraculously wake up this morning? Who did she have left to kill? Do you think, perhaps, it was someone who stood between her and the entirety of the family fortune?"
- ―Sherlock to Rebecca about Yvette
Yvette was born with a fraternal twin, Rebecca Ellison. While almost nothing is known about their childhood, they received a copy of the book The Wizard of Oz as a 5th birthday present.
On his deathbed, Yvette and Rebecca learned from their father, Charles Ellison, that they have two half-siblings, Casey McManus and Anna Webster, and they knew the two half-siblings, should they ever discover their father's identity, could sue for some of their father's inheritance. While Rebecca wanted to share the money, Yvette did not. They had their lawyers learn more about them, but before they could decide anything, Yvette started seeing a married man and drinking heavily. One day, Yvette was found comatose after seemingly trying to kill herself.
While in a coma, Yvette would receive visits from Rebecca, who would read to her. Two days after her suicide attempt, Casey McManus, one of the two illegitimate children, was killed with a gunshot to the head from a seated woman wearing T-Blossom deodorant. The next day, Sherlock Holmes, Joan Watson, and Marcus Bell, who were working the case, confirmed that a witness saw her, but only found her in a coma. When Bell left, Holmes confirmed that she was also wearing T-Blossom deodorant and he and Watson tested if she was really in a coma, which she was.
That night, Anna Webster, the other illegitimate child, was killed the same way that Casey was. After Rebecca Ellison was released from custody after being taken in as a suspect. She stopped by the hospital to read to Yvette. While there, Sherlock stormed in and claimed that he knew she was really guilty and that he knew of a third heir, Mary Margaret Phelps, and where she lived, baffling Rebecca. Detective Bell came in and Sherlock hit him, landing Sherlock in jail for the night.
Later that night, Mary Margaret Phelps was followed into her home, which is later revealed to be a trap set by the police. The follower turns around to show that it is none other than Yvette. Rebecca comes down to the station to see this, much to her shock and confusion. She learned from Watson and Holmes that the married man her sister was seeing was her doctor, and that she persuaded him to help her stage a suicide attempt and ease her into a coma, which he could easily wake her up from. This was all a part of her master plan to kill Casey and Anna to keep them from getting their share of the family fortune.
Holmes told Rebecca that she had a big heart for wanting to share the money, which is the only reason Yvette would go to such lengths. He also told her that the whole scene at the hospital was all staged so Yvette's doctor would have an address for a "third heir" to lead them into a trap.
Rebecca was about to call their attorneys to try to help Yvette, declaring that she is still her sister, but Sherlock reminded her that there were only two illegitimate children and Yvette killed the second one the previous day. He then asked why she was still comatose today and did not "miraculously" wake up. She must have had another person she planned to kill, like someone who stood between her and the entire fortune, i.e. Rebecca herself. Rebecca then looked at her sister, who looked back at her. Sherlock left her by advising Rebecca to mind her big heart and it will beat longer.