"The motor-horn!" he gasped. "The car I was in last night!" The detective nodded shortly, without speaking, and leaning forward, stared fixedly out of the window. A long, low-bodied limousine appeared, creeping slowly up, inch by inch, until it was fairly abreast of them. The curtain at the window was lowered, and the chauffeur sat immovable, with his face turned from them, as the two cars whirled side by side along the hard, glistening road. Blaine leaned forward, and pressed the electric bell rapidly twice, and there began a curious game. The other car put on extra speed and darted ahead--their own shot forward and kept abreast of it. It slowed suddenly, and made as if to swerve in behind; Blaine's driver slowed also, until both cars almost came to a grinding halt. Three times these maneuvers were repeated, and then there occurred what the detective had evidently anticipated. The curtain in the other car shot up; the window descended with a bang and a huge, burly figure leaned half-way out. Henry Blaine noiselessly lowered their own window, and suddenly flashed an electric pocket light full in the heavy-jowled face, empurpled with inarticulate rage. "Is that your man?" he asked, quickly. "The one with the three fingers! Yes! That's the man!" whispered the Doctor, hoarsely. "That's Mac Alarney." Blaine pressed the electric bell again, and their own car lunged forward in a spurt of speed which left the other hopelessly behind, although it was manifestly making desperate efforts to overtake and pass them. "Do you suppose he suspected our errand?" the Doctor asked. "Suspected? Lord bless you, man, he knows! He had already passed the two open cars full of my men, and the ambulance. He'd give ten years of his life to beat us out and reach his place ahead of us to-night, but he hasn't a chance in the world unless we blow out a tire, and if we do we'll all go back in the ambulance together, what's left of us!" Even as he spoke, there came a swift change in the even drone of their engine,--a jarring, discordant note, slight but unmistakable, and a series of irregular thudding knocks. "One of the cylinder's missing, sir." Ross turned to the detective, and spoke with eager anxiety. "We'll make it on five." The quiet confidence in Blaine's voice, with its underlying note of grim, indomitable determination, seemed to communicate itself to the other men, and no further word was said, although they all heard the thunder of the approaching car behind. The Doctor restrained with difficulty the impulse to look backward, and instead kept his eyes sternly fixed upon the trees and hedge-rows flying past, more sharply defined shadows in the lesser dark. Then, all at once, the shriek of a locomotive burst upon his ears, and the roar and rattle of a train going over a trestle. "The railroad bridge!" he cried, excitedly. "We're there, Mr. Blaine!"