| Significant |
|Jessica Margolis (girlfriend, deceased)|
|Appearances||The Mistress Always Spanks Twice|
|Portrayed by||Gil McKinney|
In Jessica's notes, she stated that it was in a dysfunctional relationship, and also Mistress Sapphire tells Beckett and Castle that she has seen how one of Jessica's clients returned after only a few minutes, and Jessica then sat crying in the locker room.
She informs them that the man was wearing a doctor's coat. Castle and Beckett then question him again, but he is shocked when he finds out that Jessica was a dominatrix. He seems not to have been the man in the lab coat.