he Enterprise is transporting to the neutral planet parliament peace delegates from two races which can't stand each other long enough to occupy neighboring suites, yet both want to join the Federation. Traveling trough a mysterious energy cloud, some gets aboard and keeps jumping from crew members to machinery and vice versa, as if seeking a suitable host and learning about the ship, without revealing itself. The crew catches on slowly, as nobody seems seriously affected, except Wesley's engineering mentor Singh, who is killed in a warp technology accident, but 'host' the highly intelligent entity.

Résumé de IMDb.com