Stargate Atlantis Season 3 Episode 12: Echoes



Everyone starts to see ghosts of Lanteans, caused by echoes being emitted by whale-like creatures (Flagisalis, first encountered in “Grace Under Pressure”) converging on the city. When side effects begin to occur, McKay discovers that the Ancients tried to teach the whales their language, who now try to warn them about a periodic solar flare that threatens life on the planet.