Joan had told him about her last relationship, and how she hadn't had another for years. She hadn't been looking, keeping all her hook ups casual, because her work was her life, and because getting close to someone only put them in danger and made her vulnerable. But he understood her work, her need to pour herself into it entirely. And if anyone could keep themselves safe from anyone wishing him, or her, harm, it was Martin.

Something occurred to her, and when their lips parted she stroked his cheek. "We should get on with the sex," she said, a smile playing on her lips. "But afterwards, remind me to tell you about Moriarty."

Sherlock aside, she represented the biggest threat to him and their relationship.