choosing to run from combat

[MrShine]

Hi

I've googled this to no avail (So I hope it's not a duplicate). Anyway here goes.
Say it's my turn and I end up in a fight I can't win.
Someone a lot stronger offers to help me for treasures, and I accept.
Then I discover that badstuff would cripple that stronger player horribly. Can I decide that we should attempt escape and risk the badstuff on the stronger player, even though we could otherwise have won the battle?