In this story by Robert Heinlein, a man (Dan Davis) is cryogenically frozen and wakes up thirty years in the future, only to discover that many of his inventions are quite famous. The only problem is that he doesn't remember inventing them. The last thing he remembers is being sent to the future via the long sleep, courtesy of his treacherous business partners. If he had never even written them down, how could they be here? With this and other questions in his mind, Dan begins to search for answers. The answers he finds raise only more questions. The patents were registered to one D. B. Davis.

After accidentally hearing about time travel, Dan decides that the answers to his problems must lie in the past. So, he resolves to travel back into the past and find out what happened while he slept. There is only one problem with all this: time travel is classified and the only one who can send him to the past is an old physicist who'd rather drink and talk about his life than engage in scientific studies.

The Door Into Summer was first published in 1956 in The Magazine of Fantasy and Science Fiction and was published the next year as a book by Doubleday.