He was responsible for her right conduct.

With intentions perfectly harmless, she might run into unknown jeopardy--above all, just at this time when she was taking reluctant leave of her friends.

The danger justified him in exceptional vigilance.
So, from his excursion into the realms of reason did he return to the safe sphere of the commonplace.

And now he might venture to press on towards Mrs.Conisbee's house, for it was half-past four, and already Monica must have been talking with her sister for a couple of hours.
His knock at the door was answered by the landlady herself.

She told of Mrs.Widdowson's arrival and departure.