The thought was fire.

He sprang to his feet, growling an oath under his breath.
"Take it easy," said Inspector Val, with a manner full of warning.
"Don't spoil a game just as the cards begin to run your way.

After we get our hands upon those French shares you may raise what row you like.
But take it easy now; try another cigar." The prudent sagacity of Inspector Val was not thrown away, and Richard saw the force of that gentleman's arguments.
"Tell me how you arrive at those beliefs about the note," said Richard.
"That's not so simple," returned Inspector Val.

"It's like asking a pointer to tell you how he scents a partridge.

My argument takes somewhat this route: I think the note tells the truth, as there's no reason why it should lie.