Designing an island home led to this logic puzzle. If you haven’t read the puzzle, follow this link (preferably before reading the solution below).
The ferryman takes the contractor across to the island, leaving him there, alone.
He goes back to the shore and brings the architect across to the island. But instead of leaving the architect and contractor together, he brings the contractor back with him to the shore.
The ferryman then takes the engineer across to the island, leaving him and the architect to swap recipes.
Finally, the ferryman goes back to the shore and takes the contractor across to the island.
All ends well.