He whistled constantly.

That, as Jan pointed out, was always a bad sign with Kenny.

It meant that he felt perilously transient and would rocket up in the air when a spark came that pleased him.

He had been much the same, Fahr remembered, the summer he embarked for Syria upon a tramp steamer--to the captain's frantic regret.
In the end, feeling absurdly sorry for him, Garry unwittingly sent the spark in by Pietro.
It was a letter from Brian.
"Tavern of Stars Open Country God's Green World of Spring "Dear Garry: "The purpose of this letter is primarily a favor.

Therefore without pretense I'll have done with it at once.