An intruder in a ski mask sits in Captain Tommy Gregson's house. When his wife enters, the man demands to know where her husband is, pointing a gun her way. A quick thinking woman, she hits the alarm on her car, startles him, runs upstairs locks her self in a bedroom, pulls a gun out of a drawer and shoots through the door at her assailant.
Once things settle, we find that she and the Captain are separated. Bell and Joan and Sherlock all want to help solve the case but they all feel a bit awkward.
Somehow, this leads to a discussion back at home between Joan and Sherlock on marriage, an unnatural state of affairs for human beings, thinks Sherlock. Joan just looks at him as if he were an alien and continues going through files.
Soon after, things unravel a bit and Joan and Sherlock talk about the nature of their partnership, and how it ought to be. In his mind, Sherlock appears to be sorting out for himself what makes a partnership a very useful and valuable thing, while a marriage is an outmoded sham.
Enter a third party with a relationship that is askew, an archaeologist is tied to the continued shootings of men who were working on a military detail of her dig site. It turns out the break in at the Gregson house was a mistake and his neighbor was the target. Her gentle wouldn't hurt a fly ex-husband is now secretly her partner in crime stealing from dig sites.
Sherlock isn't comfortable discussing actual relationships, but he does tentatively impart to Gregson that marriage is foolish but a partnership has much merit. He doesn't come out and say you should be your wife's partner but Gregson seems to take it to heart, going to talk with his wife and offering her more of a give and take and say in how things should go.
Interesting enough puzzle as Sherlock and Joan try to connect the killer and the victims.
I like the Captain Gregson character, excellently acted by Aidan Quinn and it was nice to see a bit of his backstory and home life.
Sherlock and his views on human relationships are as always quite bizarre. He does need a Watson to humanize him.