After having turned the lighthouse light on and off and on and off too many times, Fatou has burned out the lightbulb. Whoa, what a mess-up and she has to fix it before dad finds out. Roger to the rescue! Unfortunately, the alien has no solution. Things only get (way) worse when our heroes realize that an ocean liner, with no sweeping light from the lighthouse to guide it, is heading straight for the island and risks slicing it (the island!) in half. Fatou and Roger try several other replacement “lights” but in vain, until they discover a luminous, glow-in-the-dark seaweed that shines so brightly it’s almost as good as a lighthouse!