Overview
The Door into Summer is a science fiction novel by American science fiction writer Robert A. Heinlein, originally serialized in The Magazine of Fantasy & Science Fiction (October, November, December 1956, with covers and interior illustrations by Kelly Freas). It was published in hardcover in 1957.
The novel was made into a film by Takahiro Miki in 2020.
Plot
The idea for the novel came from an incident outlined by Heinlein later:
The novel opens in 1970 with Daniel Boone Davis, an engineer and inventor, well into a long drinking binge. He has lost his company, Hired Girl, Inc., to his partner Miles Gentry and the company bookkeeper, Belle Darkin. She had been Dan's fiancée, deceiving him into giving her enough voting stock to allow her and Miles to seize control. Dan's only friend in the world is his cat, "Pete" (short for Petronius the Arbiter), a feisty tomcat who hates going outdoors in the snow.
From Wikipedia (CC BY-SA 4.0).