Thirlwell had not admitted this to Scott, because he shrank from stating his suspicions, which were dark but vague.

Now, however, he thought he would try to formulate them and see how they looked, since he might, after all, take Scott into his confidence.
To begin with, nobody knew why Strange's canoe capsized.

Strange was clever with the paddle, and Driscoll's narrative, while plausible, left something to be accounted for.

It was improbable that he had quarreled with his partner while they shot the rapid, because their minds would be occupied by the dangerous navigation.

Then supposing that Driscoll had intentionally let the canoe swerve when they were threatened by a breaking wave, it was hard to see what he would gain.