Toto and Joel are two brothers living in an apartment in Madrid. They ask their parents for a rowing boat, even though there is no sea or river. After doing well in school, their parents reward them by buying the boat and bringing it into their apartment.
One day, while their parents are away, the boys break a light bulb and discover that light begins to flow like water. Excited, they use the boat to “sail” across the light, as if it were an ocean.
At first, it is a harmless and magical game. However, they invite other children to join, and the light continues to fill the apartment uncontrollably. Eventually, the situation becomes dangerous.
The story ends tragically when the apartment is completely filled with light, and the children drown in it along with their friends.