Catch a thief with a thief. Catch a radiophone with a
radiophone. A radiophone on wheels? That's a game two can play at. I'll
do it! To-morrow night."

Snapping up a telephone receiver he murmured:

"Central 662."

A moment later he tuned an instrument and threw on a switch; "Weightman
there?" he inquired. "Asleep? Wake him up. This is Curlie Carson. Yes,
it's important. No, I'll tell you. Don't bother to wake him now--have
him over at the Coffee Shop at five bells. The Coffee Shop. He'll know.
Don't fail! It's important!"

He snapped down the receiver. Weightman was the radio mechanic assigned
to his station. He would have unusual and important work to do that day.

He slumped down again in his chair but did not remain in that position
many minutes.

From one of the loud speakers came a persistent whisper:

"Hello. Hello, Curlie, you there?" the girlish voice purred, the one
that had whispered to him before. "I saw you to-night. That was
dangerous. Why did you do it? Nearly got me in bad. Not quite. He almost
got you."

The whisper ceased. Adjusting the campus coil Curlie sat at strained
attention.

"I wish I knew you were listening," came again. "It's hard to be
whispering into the night and not knowing you're being heard."

Curlie's fingers moved nervously over a tuner knob. He was sorely
tempted to tune in and flash an answering "O.K.," if nothing more.

But, no, he drew his hands resolutely back. It was not wise. There was
danger in it. This might be a trap. They might locate his secret tower
room by that single O.K. Then disaster would follow.

The whisper came again: "You're clever, Curlie, awfully clever. The way
you doubled over and turned yourself wrong side out was great! But
please do be careful. It's big, Curlie, big!" again the whisper rose
almost to speaking tone. "And he is a terribly determined man; wouldn't
stop at anything."

The whisper ceased.

For a moment Curlie sat there lost in reflection, then he muttered
savagely: "Oh! get off the air, you little whispering mystery, you're
spoiling my technique. Your very terrible friend didn't send any message
to-night and the one he sent before hasn't got us into any trouble. I've
got to forget you and go after this moving fellow who sends 600."

As if in answer to his challenge the loud speaker to his right, the one
tuned to 1200, began to rattle. Then, in the full, determined tones of a
man accustomed to speak with authority there came: