The plot of the story is driven by a series of causes and effects.  For example,

Cause:  The Aleuts try to cheat the islanders out of payment for the otter they catch.

Effect:  There is a fierce battle, and most of the men of the island are killed.

Cause:  There are not many men remaining on the island.

Effect:  Women must take over the traditional work of the men. 

Cause:  The memory of the treachery of the Aleuts, and the necessary reorganization of social roles on the island result in sadness and unrest.

Effect:  Kimki goes to find another country where the tribe can live.

Cause:  When the ship comes to take the tribesmembers away, Ramo is late, and ship must embark without him.

Effect:  Karana jumps off the ship to be with her brother, and both are left on the island.

Cause:  Ramo is killed by wild dogs.

Effect:  Karana is now completely alone on the island.

Cause:  Karana is lonely.

Effect:  Karana makes friends with the wild creatures that inhabit the island - an orphaned otter, two birds, and a wild dog whom she names Rontu.

Cause:  Karana feels a oneness with the natural world, and is repulsed by the memory of the Aleuts and the way they mercilessly and wastefully hunted the otter.

Effect:  Karana lives in harmony with nature, refusing to shoot a sea lion so she can use its ivory to make tools, and later spaing the life of Tutok, the enemy Aleut girl, even though she is afraid Tutok will betray her to the other Aleuts.