When you leave the airship for treasure and the captain succeeds in the next leg of the voyage you may shoot your grappling hook and get back on board. Obviously playing this special card means you'll have to leave the treasure from the previous city behind. You can't hang on to a rope without letting go of your heavy load.

Grappling hook:

Can be played by: a passenger who just left the ship

Can be played when: the captain announces that the journey will continue

Has for effect: that the passenger who plays this card may climb back on board of the air ship (whilst leaving the last claimed treasure behind)