Obsessed is most appropriate to describe a person whose mind and heart are concentrated on one idea to the exclusion of everything else.
I hope this helps you. ☺
Hiram Bingham discovered Machu Picchu on July 24th 1911
If the question is about the words "scuttled off" then the accurate answer would be imagery, more specifically, kinesthetic imagery, that is to say, imagery related to the vivid significance of the movement of the crab that implies both a physical gesture that reveals an emotional movement associated to that gesture. In literature, this is called "from motion to emotion". In this particular case, the movement of scuttling off implies that the patience of the crab is about to meet its limits and because the crab does no longer want to be subjected to an uncomfortable situation it translates its emotion into the motion of leaving. Furthermore, the following use of direct speech right after this motion completes the cycle of emotion to motion and then back to emotion.
