Uninvited

Uninvited is the fifth episode of the tenth season of Stargate SG-1.

Plot
As the rest of SG-1 prepares to join Landry (Beau Bridges) and Mitchell (Ben Browder) on a retreat, Teal'c (Christopher Judge), who is assisting the SG-3 team, discovers that the inhabitants of a distant planet are being mutilated by a savage and elusive alien creature. While SG-1 fears the Ori's sinister work is at play, they soon discover the creatures are being mutated by a parasite not indigenous to the planet.

Meanwhile, Mitchell and Landry are the object of surveillance while staying at General O'Neill's cabin. As SG-1 receives word that the creatures are appearing on other planets also, Mitchell discovers some hunters who have been the victim of a similar attack on Earth. Desperate to find the origin of the parasites, the team makes an alarming discovery: not all planets affected by the attacks were visited by the Ori, but they were all recently visited by SG Teams using Sodan Cloaking Devices. Horrified to discover that they could somehow be to blame, SG-1 must determine how to stop the creatures before they kill again.

It is discovered that the strange parasites are slipping into the world from another dimension when the cloaking device is activated - it works by putting the user out of phase with our dimension. Furthermore, it is discovered that a Trust operative is using a stolen cloaking device on Earth, explaining the presence of mutated creatures. Carter discovered that the cloaking devices originally included a safeguard - a form of radiation that repels the parasite but is harmless to the Sodan. However, long term exposure was harmful to humans, so the safeguard was overridden - without knowing about the parasites. Stargate teams on earth are able to use this radiation to contain the creatures and eventually kill two of them, which are believed to be the only ones.

SG-1 celebrates a job well done by playing poker - Vala being a natural gambler, but Mitchell comments that she watched the 'poker channel' too much.