Who could prove the truth?
The boy and girl might have a secret to keep; she might have arranged to get him into the hospital because it was his only chance, but the rest of the story, such as it was, might be a pure invention; and when Marcello was discharged cured, they would disappear together.

There was the coincidence of the baptismal name, but men of science know how deceptive coincidences can be.

Besides, the girl was very intelligent.

She might easily have heard about the real Marcello's disappearance, and she was clever enough to have given her lover the name in the hope that he might be taken for the lost boy at least long enough to ensure him a great deal more comfort and consideration in the hospital than he otherwise would have got; she was clever enough to have seen that it would be a mistake to say outright that he was Marcello Consalvi, if she was practising a deception.

Kalmon did not know what to think, and he wished the operation could be performed before Corbario came; but that was impossible.
Regina stood beside him, waiting for him to speak again.
"Do you need money ?" he asked abruptly, with a sharp look at her face.
"No, thank you, sir," she answered.