Anna Sinclair is one of Lord Sinclair's children. When her father was murdered, she was one of the suspects. She used to live in Camelot castle, but when King Arthur and his knights arrived, Lord Sinclair and King Ulthas agreed that the knights had greater need of the castle and so the Sinclair family moved to Sinclair Mansion instead. This greatly angered all of his children. Like her siblings, Anna has a silver-coated item, in her case a necklace.
She is fond of sewing and gardening. At one point, she had a relationship with Stanford the gardener, but when it ended she tried to get him fired by killing the flowers. This caused Stanford to consider her to be the killer. At some point, she bought some poison from the Poison Salesman to kill some maggots on the compost heap. If there are still maggots on the compost heap, she is the murderer.
She later conspired with her siblings to get Camelot back from King Arthur and the Knights of the Round Table. They allied themselves with Morgan Le Faye, hired some Kinshra knights from Lord Daquarius, and stormed the castle, taking the knights and the wizard Merlin prisoner. They also threatened the staff, telling them that they would die if they left or spoke to anybody not of the family. They then framed Anna for their father's murder, trusting that the investigator would get her free, and moved out of the mansion and into the castle. She offered to help the investigator get into Camelot if they managed to free her. The investigator then proved that the evidence against her was not definitive - the thread could have been either Anna's or David's; each sibling bought enough poison to complete their task and poison their father; Frank had also handled the dagger; one of her brothers was seen at the murder scene - and she was pronounced not guilty. She showed the investigator how to get into the castle then betrayed them to Morgan Le Faye. After the knights managed to free themselves, Merlin scared them off and threatened to turn them into rabbits if they tried anything again.