Write a sentence to introduce the main character in a novel.
John Doe was a young man with a mysterious past whose only ambition in life was to solve the impossible.
Below is an instruction that describes a task. Write a response that appropriately completes the request.

### Instruction:
Write a sentence to introduce the main character in a novel.

### Response:
John Doe was a young man with a mysterious past whose only ambition in life was to solve the impossible.