It sounded strangely familiar, that number! He repeated it over again slowly: "One-five-eight-three-six." And the smile left his lips, and upon his face came the look of a chastened child.

She had used a duplicate plate! Fifteen thousand eight hundred and thirty-six was the number of one of his own cars--his own particular runabout! For a moment longer he stood there, undecided whether to laugh or swear, and then his eyes fastened mechanically on the envelope he was twirling in his fingers.

Here, at least, was something that was not elusive; that, on the contrary, as a hundred others in the past had done, outlined probably a grim night's work ahead for the Gray Seal! And, if it were as those others had been, every minute from the moment of its receipt was precious time.

He stepped under the nearest street light, and tore the envelope open.
"Dear Philanthropic Crook," it began--and then followed two closely written pages.

Jimmie Dale read them, his lips growing gradually tighter, a smouldering light creeping into his dark eyes, and once he emitted a short, low whistle of consternation--that was at the end, as he read the post-script that was heavily underscored: "Work quickly.
They will raid to-night.