First published as La Chiave a Stella by Einaudi in 1978 the book was written after Levi had retired from SIVA. It takes the form of an interview by a chemist of a rigger. They are both working in a remote work camp where there is little to do in the evenings except tell stories. The scene is loosely based upon Togliattigrad, the Fiat camp set up in Russia to build a car factory. The rigger is Libertino Faussone and the chemist is clearly autobiographical.
The job of a rigger is to set up cranes and scaffolding and to manage major mechanical projects. One of Faussone's jobs is to sort out a problem with an acetic acid separation column which goes through a cycle of making loud noises and shaking, before settling down again. It turns out the ceramic contents of the column have disintegrated and have formed a sludge at the bottom. This is precisely what happened at SIVA to a column that Levi designed.
Levi always felt that satisfying work was essential for a happy life, and the honest hands-on work of someone who also used his intellect was the highest form of work. Faussone was his ideal. Life is a series of problems which one has to use ones brains and ones hands to resolve.