 Lie left for Fontainebleau where after a while he was arrested under suspicion of being a German spy, an event that made him famous in Norway.He was released from prison after a month, thanks to the intervention of Darboux.Lie obtained his PhD at the University of Christiania (present day Oslo) in 1871 with a thesis entitled "Over en Classe geometriske Transformationer" (On a Class of Geometric Transformations).