a good candidate in Mr. Hallam? The grammar?

As I could understand, Dr. Owen had a candidate called Mr. Hallam. So I failed to get what "in" means there.

Context:

He has served in the French Parliament since 1986. His interest in politics, he said, comes in part from memories of his family's involvement in the French resistance movement.

When Dr. Dubernard could not find a candidate for a hand transplant in France, he turned to his friend, Dr. Earl Owen of Sydney, Australia, who shared a goal of transplanting a hand. Dr. Owen had what the team believed was a good candidate in Mr. Hallam.
More:
http://www.nytimes.com/2005/12/06/science/06prof.html?pagewanted=2