What is "l'ouvretemps"

L'OuvreTemps (English: The Time Opener) is volume twenty-one in the French comic book (or bande dessinée) science fiction series Valérian and Laureline created by writer Pierre Christin and artist Jean-Claude Mézières. It continues the story begun in At the Edge of the Great Void and continued in The Order of the Stones. It was released in January 2010. It is the last volume in the series.