Then, too, several times in the crowded subway cars she had noticed a face that was familiar.

It was Drummond, never looking directly at her, always engrossed in something else, yet never failing to note where she was going.

That must be, she reasoned, some of the work of Beverley and Dumont.
Murray was now working feverishly.

As he worked he found himself feeling differently toward the whole affair.

He actually came to enjoy it with all its risks and uncertainty, to enjoy gathering the data which, he should have said, ought really to be destroyed.