In the meanwhile my mind had not been idle, and I had finally evolved an idea.

Jacobus Laningdale's head was very like any other head, but in that head was evolved an idea.

But by and by I evolved an idea- Iwouldwake my brother and probe him with a supposititious case.

Laura Belding had evolved an idea regarding "Mr. Nemo of Nowhere," as Bobby dubbed the stranger at the hospital.