He pointed to the huge oaken door and Frank saw that it was ajar. The snow on the porch was not deep and they saw that footprints led from the open door to a corner of the porch. At that point the snow on the railing was disturbed, as if a hurrying man had clung to it a moment before jumping over and into the drifts below. But the tracks led no further, for the drifting snow had covered all excepting a hollow where some body had landed. "Thomas!" exclaimed Frank. "And he was in a hustle, by the looks of the tracks. Bet he was frightened while at the telephone and beat it." They entered the house and closed the door behind them. It was growing quite dark and Frank searched for the light switch. This was near the door, and, at pressure on the upper button, the spacious old hall with its open staircase was revealed dimly by the single remaining bulb in a cluster set in the center of the high ceiling. The hall was unfurnished, excepting for a telephone table and chair, the chair having fallen to the floor and the receiver of the telephone dangling from the edge of the table by its cord. "You must have heard the chair fall," commented Tommy, "and it sure does look as if Thomas left in a hurry. Wonder what it was that frightened him?" The house was eerily silent and the words echoed awesomely through the adjoining rooms which connected with the hall through large open doorways. "Spooky place, isn't it?" returned Frank. * * * * * And then they were both startled into immobility by a rumble that seemed to shake the foundations of the house. Heavier and heavier became this vibration, as if some large machine was coming up to speed. Louder and louder grew the rumble until it seemed that the rickety old house must be shaken down about their ears. Then there came a whistling scream from the depths of the earth--from far underground it seemed to be--and this mounted in pitch until their eardrums tingled. Then abruptly the sounds ceased, the vibration stopped, and once more there was the eery silence. Rather white-faced, Tommy gazed at Frank. "No wonder old Thomas beat it!" he said. "What on earth do you suppose that is?" "Search me," replied Frank. "But whatever it is, I'll bet it has something to do with Leland's strange actions. And we're going to find out." He had with him the large flashlamp from the car, and, by its light, the two made their way from room to room searching for the iron-bound door mentioned by Thomas. They found all rooms on the first and second floors dusty and unused with the exception of two bedrooms, the kitchen and pantry, and the library. It was a gloomy and spooky old house. Floor boards creaked startlingly and unexpectedly and the sound of their footsteps echoed dismally. "Where in time is that laboratory of Leland's?" exclaimed Frank, his ruddy features showing impatient annoyance, exaggerated to an appearance of ferocity by the light of the flashlamp.