Danny Dunn and Heat Ray

Danny is soaring above Midston in a plane with his pilot friend when he catched sight of a man stranded in a field and helps rescue him. The man happens to be millionaire Gledway Pippit, who is interested in Professor Bullfinch''s new heat ray -- but Danny and the Professor must prove to him that the invention can be useful.

One afternoon, Danny''s friend Irene is listening to her short-wave radio ...