At Father Flood's Christmas meal, what is it about one of the guests as he enters that startles Eilis(Although she later realizes she is wrong)?

A man comes in for dinner, who Eilis is certain is her father. She is wrong.

"He stood still as soon as he had closed the main door behind him, and it was the way he took in the hall, surveying the scene with shyness and a sort of mild delight, that made Eilis sure, for one moment, that he father had come into her presence."