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.
Hired Girl, Inc. manufactures robot vacuum cleaners, but Dan had been developing a new line of all-purpose household robots, Flexible Frank, when Miles announces his intention to sell the company (and Flexible Frank) to Mannix Enterprises in which Miles would become a vice president.
Left with a large financial settlement, and his remaining Hired Girl stock, he elects to take "cold sleep" (suspended animation), hoping to wake up thirty years later to a brighter future.
First he mails his Hired Girl stock certificate to the one person he trusts, Miles' stepdaughter Frederica "Ricky" Virginia Gentry.
He has lost Pete the cat, who fled Miles' house after Dan was drugged, and has no idea how to find a now middle-aged Ricky.
At that point Dan finds that Ricky has been awakened from cold sleep and left Los Angeles for Brawley, California.
He sets up a new corporation with the Suttons called "Aladdin Auto-engineering", returns to Los Angeles, and stakes out Miles' house on the fateful night.
Watching himself arrive, he lets events unfold until Pete the cat emerges, then takes his own car and uses it to remove Flexible Frank and all his engineering drawings from Miles' garage.
Destroying the drawings and scattering machine parts across the landscape, he heads out to meet Ricky at her Girl Scout summer camp.
Setting himself up as an independent inventor, he uses Ricky's Hired Girl stock to make changes at Geary, settling back to watch the healthy competition with Aladdin.
The idea recurs in the 1964 novel Farnham's Freehold, which hurls its protagonists into the future and then returns them to their own time, where they alter their destiny.
The United States was the clear victor, thanks to technologies that include the "cold sleep", which was used to maintain a large standing army that could be revived quickly and put into the field.
The United States rapidly recovers, refugees from devastated areas move to unharmed places, especially California, and the nuclear war leaves no lasting trauma.
"[4] Science fiction writer and critic James Blish, writing in 1957, shortly after publication, criticized the lack of characterization of its hero Dan Davis, saying, "It is surely an odd novel that is at its best when the author is openly editorializing ..." — in this case about the "parity system of farm price supports, which in 2000 is applied to automobiles.
... Every other important subject of science fiction which Heinlein has examined at length has come out remade, vitalized and made the author's own property.
"[9] CREDEUS Inc. adapted the novel into the feature film 夏への扉 キミのいる未来へ (The Door into Summer), which was directed by Takahiro Miki and released on February 19, 2021.
[10] In 1967, the American rock group The Monkees, recorded the song "The Door into Summer" for their album Pisces, Aquarius, Capricorn & Jones Ltd.
In a livestream interview in 2020, Nesmith directly attributes the inspiration for the song to the story about Heinlein's cat looking for the "Door into Summer".