What confuses you is this. Henry grew up in this house. He's known this staircase since he was a kid, like every corner of his house. He could have walked blindly through the whole house in the dark, no doubt about it. So something must have happened that day. Something unusual, out of the ordinary. Ask the people present a question about it. What was different about that day than it always was?
LIST OF PERSONS WHO WAS IN THE HOUSE AT THE TIME OF THE INCIDENT: