Its four small panes were separated by a wide old-fashioned cross-piece of hardwood and putty.

The putty, from age, was as solid as cement.

The whole window was a bare sixteen by twenty inches.
Lad ran back, once more, a few feet; his gaze fixed appraisingly on the window and measuring his distance with the sureness of a sharpshooter.
The big collie had made up his mind.

His plan was formed.

And as he was all-wise, with the eerie wisdom of the highest type of collie, there can be scant doubt he knew just what that plan entailed.
It was suicide.