Fourteen-year-old Jake is forced to be left to live at a retirement home in Poughkeepsie, New York while his father, Dr. Robert Lansa, travels to help his friend Bill set up a jaguar preserve.

Doc, as everyone calls him, takes longer than expected in Brazil and sets up a plane ride for Jake to visit during his Spring Break.

When he arrived in Manaus, Jake met Buzz, the expedition's pilot who is supposed to track jaguars at the preserve.

Silver secretly knows about the man with the scar and encourages everyone to keep a shotgun nearby on the boat.

Doc meets with the Indian, Raul, who helps him tranquilize the jaguar under the conditions that he gets to come on the expedition to see it let go and that it gets weighed.

Things are going well until Doc and Raul take a week-long trip to the rain forest and Silver disappears.

They rescue Raul, captured by the isolated Indian camp and they trap Tyler using the killed jaguar's collar.

He falls into a pit and after a brawl with Raul and Jake, Silver has to drop his gun and step back.

The night before they would leave the lake and find another place to set up camp, Woolcott, the one who is willing to fund the preserve, along with Buzz, lands in a very nice floatable private plane.

Kirkus Reviews called the book, "A first-rate adventure about greed, mutual dependence, and family".