"How do you make that out?" asked Jones.
"Lee thought he heard a step on the walk and assumed that it was the girl leaving the grounds. He hurried to the gate, but when he looked around there was no one in sight. If she had really left the place he would have been in time to see her as she walked down the block. There would be no place for her to disappear to unless she jumped in the river, which would hardly be likely."
"She may have hidden in the grounds and have waited for Lee to go away first," I objected.
"She did not know he was there and would have no reason then for hiding. No, no, she's at the Darwin house. It was the easiest place to hide her in, safe and secure, and it would not involve his having to take anyone into his confidence. The house, doubtless, has more than one secret room. We'll go out there now, and in an hour we'll have her free."
"Do you want a taxi?" asked Jones.
"No, we'll use the subway this time," replied McKelvie.
We walked to Union Square and took the Broadway Subway to Dyckman Street, walking from there to Riverside Drive. As we entered the Darwin grounds I paused to admire the brilliancy of the stars, and noticed how the reflection of the lights from the river craft twinkled in the waters of the Hudson as if in friendly rivalry.
But my companions did not wait to look at the scenery, and I had to hurry to catch up with them.
"We'll go in the back entrance again," said McKelvie. "I want to question Mason."
After a slight delay the old man admitted us and McKelvie asked him if he ever took occasion to go into the main wing of the house.