Mysteries and horses

Hi folks,

I have a challenge for you. I'm after mystery novels that centre around horses, ideally if:

1. The horse in question goes missing;
2. The story is not centred around the racing industry – there's plenty of those, so I'm looking for a more unusual situations, such as a farm horse, war horse or family pet; and
3. Not Dick Francis 😉

Bonus points if it's a historical mystery, but modern day is good too!

Thank you!