An alien space probe of unknown origin, the Probe wreaked ecological havoc on planet Earth when, in 2286, it came searching for humpback whales. The Probe wanted to contact the intelligent species, but unfortunately the humpback had become extinct in the 21st Century, so there were no whales to contact.

The damage to Earth's biosphere occurred when the Probe failed to make contact, and thus increased the power of its carrier wave to dangerous levels. Its carrier wave, its signal, emitted from a revolving, luminescent sphere, somehow suspended beneath the Probe.

Disaster was averted when Kirk and his officers used a stolen Klingon Bird-of-Prey to travel back in time, to the 20th Century, and bring back with them two humpbacks to answer the Probe.

The Probe received their whale song and returned from whence it came.