I had a brilliant game of Mansions of Madness, but reached the Ungoal when my monsters couldn't get a final sample dropped onto the altar and both players' and keeper's characters hearts exploded. Oops.

Anyway, we had to make a quick ruling about something which cost me the game. I was fine with it in the moment, but for future reference, wanted to clarify something.

"Take Sample" says that if a monster's in the altar's space at the start of the turn then the sample they delivered is put on the altar and I gain threat. If said monster is stunned, we didn't have that trigger, as it made a narrative sense. Still, I was wondering if there was a rule we missed or what other people have ruled as far as this example.

I hope that was spoiler-free enough, other than that in one option of one story, your heart may explode. This is Lovecraft, that's probably the best thing you can hope for in most games.

Well, given that stunned monsters can still take samples (but can't do the move one space after TS), I wouldn't block samples from being placed by stunned monsters. Maybe it stumbles around in a drunken haze and bumps into the altar, dropping the sample on the spot .

No ruling against dropping samples with stunned monsters. Also, the trigger is "start of the keeper's turn" and does not necessarily have anything to do with the monster. Well, except for the other part with "if a monster is at an altar", of course.