Nick, a famous stand-up comedian, agreed to host a telethon for the Society of Cats at half his usual $10,000 fee. Nick and the Society of Cats signed a contract. The Society of Cats expected to raise $100,000 from the telethon. A week before the telethon, $5,000 was paid into Nick's bank account. Nick had spent many hours working up jokes about the Society of Cats, since his regular materials were not really suitable for the expected audience. On the morning of the telethon he awoke with laryngitis and no voice, and the doctor told him cannot perform. The contract did not say anything about inability to perform.

The Society of Cats found a less well-known comedian to host the telethon and raised $10,000.

Did Nick have to return $5,000 to the Society of Cats? Why or why not? Define legal concept(s) and principles that you use.