The box was heavy, but perhaps a flood had rolled it down the rapid, or it had fallen from Strange's pocket when the stream washed his rotting clothes away.
Thirlwell shook the box and something rattled inside, after which he noted a dark smear round the edge of the lid.

He scraped this with his knife and thought the stuff was a waterproof gum the freighters used to caulk their canoes.

It looked as if Strange had carefully made the joint watertight, and Thirlwell's curiosity was strongly excited, but the box was not his.

It was too early to look for Agatha, and he waited with some impatience until she came out of the shack and sat down in the sunshine after breakfast.
"I think this was your father's," he said, putting the box in her hand, and told her how he had found it.
Agatha started.

"Yes; I gave it him on his birthday long since.