This time, the searchers bring along the famous half-White and half-Indian African mercenary Charles Munro, as well as a female mountain gorilla named Amy, who has been trained to communicate with humans using sign language, and her trainer Peter Elliot.

Time is of the greatest essence, as a rival consortium from corporations in Japan, Germany, and the Netherlands are also searching for the diamonds, turning the entire expedition into a race to the city of Zinj.

They also exhibit behavior unlike normal gorillas: they are highly aggressive, ruthless and partially nocturnal, as well as extremely social, forming troops of over a hundred, compared to a mere dozen animals.

Afterwards, Ross, Elliot, and Munro explore the ruins and discover that the killer gorillas were bred by the ancient inhabitants of Zinj to serve as guards to protect the diamond mines from intruders.

Their victory is cut short by the eruption of the nearby volcano (accelerated by explosives placed by Ross for her geological surveys) which buries the city, the diamond fields and all proof of the "new" species under 800 meters of lava.

In an epilogue, it is revealed that Munro was able to retrieve 31 carats of the valuable diamonds and sold them to Intel for use in a revolutionary new computer processor, while Amy was reintroduced into the wild and was later observed teaching her offspring sign language.

In 1995, a film version of Congo was released, directed by Frank Marshall and starring Laura Linney, Dylan Walsh, Ernie Hudson, Tim Curry, Grant Heslov, Joe Don Baker, and Shayna Fox as the voice of Amy.