This swung the nail to and fro, and it tapped on the window-pane as if some one was throwing pebbles against the glass.

This was kept up for several seconds.
The widow, who was reading in the dining-room, heard the tapping at the glass.

It startled her at first, and then, thinking some one might be at the door, she conquered her nervousness and opened the portal.

Of course she saw no one, and the string was not observed.
Neither were the boys, hidden in the bushes.
"We fooled her," chuckled Ted, for they could see all that happened.
"Sure we did," added Bob.

"Wait till she goes in and we'll do it some more." Somewhat puzzled, the Widow Mooney closed the door.