Who had the contract in the abandoned shack?

In the Dark Brotherhood mission where you have to kill one of the three people in the room: the Khajiit guy who was pretty cool, the mercenary who was pleading and a woman who was running her mouth at me. I killed the woman in the end.

Who actually had the contract?

Solution 1:

While it's almost certain they all had contracts out on them, Astrid does prefer you killing one particular person over the others:

Vasha, the Khajit, describes himself as a murderer, a rapist, and a thief. If you kill him, Astrid remarks that he was the obvious choice.

However, if you kill all of them, she'll make a snarky comment that you're an overachiever.

But as you'll soon find out—should you choose to join the Dark Brotherhood—the contracts placed are, many times, non-obvious and counterintuitive.

Basically, the point of the abandoned shack test is to get you to kill on command: if the Family says someone needs to die, that person needs to die, regardless of what excuse they give you or backstory they have.

Solution 2:

If you use the Clairvoyance illusion spell, it leads you to the Khajiit. Whether it's because he's the real contract, or if he just happens to be were the "location marker" of the quest is, I don't know. I would expect it to be him, or the Mercenary. The woman would makes sense too, as stated above the reasons for contracts are sometimes quite petty and ridiculous. I always choose the Khajiit. Not only does he threaten you (if you don't let him go), but he talks about all the disgusting actions he's been apart of.

I would say that it doesn't matter who has the contract. You aren't meant to know, so as in a real life situation such as this, might as well kill the one you THINK it is and keep a peaceful state of mind by believing you were right.