Lane answered his unspoken query.

"Yes, that's right. Ventilation. These devils may be inhuman in form but they're clever. They've built this underground city, equipped it with heat, light, ventilated it to maintain circulation—"

There was something wrong there. Tim frowned.

"Ventilation? Yet you say that stream is ammoniated enough to kill a man. Then how do they live?"

"They're not men," replied Lane bitterly. "They're vampires. Heaven knows how they can breathe this atmosphere, but they can. The ingenious, murdering..."

He didn't complete the sentence. For at that instant there came the scrape of movement outside their dungeon door. The door swung open. A bat-man entered. His hooked claw signalled them to come forth. Tim glanced at the older man. Lane shrugged resignedly.

"There's nothing else to do. Maybe we can strike a bargain with them. Our freedom for something they want."

But there was no hope in his voice. Tim threw an arm about Dorothy's shoulders. They followed their guide out of the room. There a cordon of other bat-creatures circled them, and Tim, for the first time, got an opportunity to see his captors at close range.

They weren't much to look at. They were such stuff as nightmares are made of. Tall, angular, covered from head to toe with a stiff, glossy pelt of fur. Their faces were lean and hard and predatory; their teeth sharp and protruding. Their wings were definitely chiropteric; the wing-membranes spanned from their shoulders to their claws, falling loosely away when not in use, and were anchored to stiff, horny knobs at clavicle and heel.

They walked now, guarding their captives, but it was apparent that flight was their usual method of locomotion. Anything else would be awkward, for their knees bent backward as did the knees of their diminutive Earthly prototype.

They turned, at last, into a huge chamber. And before them, perched obscenely on a platform elaborately laid with jewels and tapestries, was the overlord of the Harpies.

No man, by the wildest stretch of the imagination, could have considered any of the vampires attractive. But of all they had seen, this monster was the most repugnant. It was not only that his frame was tauter, skinnier, than that of his fellows; it was not that his furry 

 Prev. P 15/21 next