A question for German speakers

I work in a library, although I don’t work for the library. The loading dock entrance is where I leave and enter the building, and it’s also where donated books are placed prior to sorting.

Today I was there when someone brought in about seven boxes of book most all in good shape, of which 95 percent seemed to be science fiction and fantasy. There were a number of classic authors, including a ton of Heinlein paperbacks, in the covers I remember from when I was first reading Heinlein

But one was peculiar, it was a translation into German of one of Heinlein’s books. I don’t read a word of German, and the picture on the cover was not from any story line I recall, I think the publishers must have just wanted something strange.

If I recall correctly, it was somethink like Die Sechste Kolonne. I’m not sure about the spelling. Does anyone have a clue to which title this is?

I have limited German, but it’s Sixth Column, “also known under the title The Day After Tomorrow”.

See, this is why I love this board!

Thank you so much. I read the book under the latter title, although I knew it had been retitled.