Most of the time, when people say they're sorry for things that have happened as opposed to things they've done, Sherlock's response is to snap at them or make some sort of acidic remark about how culpable they actually are.

But when Molly says it, he thinks he understands what she's getting at. She's trying to take a little of the weight away, to let him know that this loss doesn't frighten or disgust her.

And it works.

He turns his hand, long fingers sliding through hers, holding on.

"Thank you, Molly."