Murder is lovely, of course, but it would be absolutely fine if Troy just painted Harriet's portrait and they compared notes on being murder suspects and wives of detectives.

I don't think they should have to be suspects again. I don't think either of them would appreciate it, and Troy never enjoys having to get people hanged. There could be theft or minor crime and everyone expects them to solve it because of their connections.

Or murder, obviously. They are plagued by murder - Harriet falls over bodies on beaches and Troy can't get on a canal boat without encountering one. :-)

(BUt I'm just saying, I would also enjoy just them meeting for coffee in a ficlet or anything really as long as it was a thing.)