The Door into Summer

I have finished reading the novel "the door into summer" by Robert A Heinlein. This was a great time travel novel, with an engineer with lots of ideas for novel for robotics. But what haunts m the most was the starting story. In the winter, a cat is going round the house trying all the different doors. The cat is hoping to find the door into the summer.

Of course there is a strange "love" affair in the novel, that looks wrong.