Describes the role of apex predators, such as wolves, in an ecosystem and how introducing wolves back into Yellowstone National Park restored a greater diversity of animals, plants, and insects into the area. Includes illustrations and a glossary.

An unintentional experiment -- Taming the wild -- The food web -- Silence in the valley -- Portrait of a wolf ... -- And its pack -- A predator moves in -- An ungulate buffet -- Tree transformation -- Business as usual for bison -- Canids in the middle -- Sky full of predators -- Feathered frenemies -- Grizzled giants... -- And creeping crawlies -- The valley sings again -- The return of the beaver -- Mending the web.