We were at some luxury hotel and people kept dying horribly. I think four or five people had died when the countess (a spry 70 year old woman) went to jump on her white horse which was waiting for her in the courtyard. The killer had loosened the saddle so she fell and broke her neck. We were all horrified. And I knew who'd done it. I'd seen her loosen the saddle and hadn't thought anything of it at the time and it all happened so fast, while I wasn't paying attention that I didn't realize the countess had attempted to mount the horse until she had fallen off. Looking at the other people assembled in a line in the courtyard I realized another woman had realized it too. The killer (also a woman) walked past and the person who'd had the revelation stopped her and whispered that she knew the woman was the killer. I didn't wait to see if it was a warning to stop (which I assumed it was), but went immediately to Poirot who was standing near the opposite end of the line and told him what she'd said. Then the killer confessed in front of us and grabbed a branch off the nearest tree and started swinging it wildly. Poisonous thorns. She managed to scratch me in two places, high on my left arm, and my right forearm. At first I didn't think she'd gotten me, then I started to feel my tongue and limb deaden and feel very heavy. I valiantly struggled on to curse at her, give her the double-handed, single-finger salute and go to grab a branch off the tree and poison her right back, when Poirot stops me and explains that the medics are on their way and I don't want to be murderer, even of a murderer, when I'm better. Then the other woman, who'd stopped the killer and told her knew what she'd done, grabbed a knife and went after the killer. The killer turned the knife on her.
Then one of the women went back in time to before the first 5 victims were killed and pulled a knife on her in the same courtyard and the same thing happened, but this way, her evil plans to kill all the people who were mean to her were foiled.