"Alice" is sold by Count D to a couple who recently lost their daughter also called Alice. He calls it "a very rare species of rabbit". But when he shows "Alice", she doesn't appear very rabbit-like at all. It actually looks exactly like the rich couple's recently deceased daughter Alice.
The couple probably suspects human trafficking, but they are very happy to almost have their daughter back. So they buy her instantly, and with that signing a contract with the count.