James felt that his Patronus's journey was nearing its end, but he grew more and more frightened when he didn't hear Harry's coos or cries. His son was just a baby, there should be some sort of noise associated with child that young.
What he saw, what he heard when Lily spoke and the Patronuses dissolved, left him stunned. This man was older than he was, and so unlike the baby that he remembered at first glance that it seemed impossible. His son was small enough to be lifted easily, and this man was clearly grown up. Harry's hair was beginning to get a bit of the typical Potter unruliness, but it still had a bit of baby softness to it, and this man's hair looked unmanageable enough to devour a small child.
"Harry?" James questioned, a baffled look on his face.
He just stared between Lily and the stranger for a moment, and then the pieces began to fall into place. James took in the stranger's dark hair and green eyes, the glasses that were a bit like James' own, the way that Lily's tears were mingling with laughter instead of despair. Was this possible? Part of him was overjoyed that his son had lived so long, that he was safe and alive and well by the looks of it, and part of him was suffering from an unpleasant shock. If this was his Harry, if he was a grown man, James and Lily had missed a good deal, what could arguably be called the best years of Harry's life. They were all alive, but what sort of life had they been brought back to?