"Well--" I began.

"You must, George. Babs and I need you. See here--"

He tried at first to make it sound like an invitation for a New Year's
Eve holiday. But I knew it was not that. Alan and Barbara Kent were my
best friends. They were twins, eighteen years old. I felt that Alan
would always be my best friend; but for Babs my hopes, longings, went
far deeper, though as yet I had never brought myself to the point of
telling her so.

"I'd like to come, Alan. But--"

"You must! George, I can't tell you over the public air. It's--I've
seen _him_! He's diabolical! I know it now!"

_Him!_ It could only mean, of all the world, one person!

"He's here!" he went on. "Near here. We've seen him to-day! I didn't
want to tell you, but that's why we came. It seemed a long chance, but
it's he, I'm positive!"

I was staring at the image of Alan's eyes; it seemed that there was
horror in them. And in his voice. "God, George, it's weird! Weird, I
tell you. His looks--he--oh I can't tell you now! Only, come!"

* * * * *

I was busy at the office in spite of the holiday season, but I dropped
everything and went. By one o'clock that afternoon I was wheeling my
little sport midge from its cage on the roof of the Metropole
building, and went into the air.

It was a cold gray afternoon with the feel of coming snow. I made a
good two hundred and fifty miles at first, taking the northbound
through-traffic lane which to-day the meteorological conditions had
placed at 6,200 feet altitude.

Flying is largely automatic. There was not enough traffic to bother
me. The details of leaving the office so hastily had been too
engrossing for thought of Alan and Babs. But now, in my little pit at
the controls, my mind flung ahead. They had located him. That meant
Franz Polter, for whom we had been searching nearly four years. And my
memory went back into the past with vivid vision....

The Kents, four years ago, were living on Long Island. Alan and Babs
were fourteen years old, and I was seventeen. Even then Babs
represented to me all that was desirable in girlhood. I lived in a
neighboring house that summer and saw them every day.

To my adolescent mind a thrilling mystery hung upon the Kent family.
The mother was dead. Dr. Kent, father of Alan and Babs, maintained a
luxurious home, with only a housekeeper and and no other servant. Dr.
Kent was a retired chemist. He had, in his home, a chemical laboratory