The missing page

An original fiction passage set in the nineteenth century.

Mr Crane searched the ledger again. The torn edge was unmistakable: somebody had removed the page after the accounts were written. He shut the book when his assistant entered and began discussing the weather. His voice remained cheerful, but his fingers tapped an impatient warning against the cover. The assistant offered to fetch yesterday’s receipts. Mr Crane thanked him, watching the young man’s face more closely than the suggestion required.

Identify the phrase which suggests that Mr Crane’s movements reveal anxiety.