Secret of the River by Fred M. White

The mere fact that Murray and Sidey were frequently absent in London on business had not prevented Nevil from striking up some sort of a friendship with Blanchin. It was to the latter's interest to encourage the old gentleman, but it was nearly the end of a week before Blanchin seemed inclined to fall in with the professor's hint that the latter might be permitted the favour of a visit to the laboratory.

This came about on the following Friday afternoon, not long before Murray and Sidey were expected home from town for the week-end. They were also expecting a visitor, Blanchin explained, who was coming down by car.