Entity

S4, E20: Stargate Command is infected by an alien probe that uploads its program into the base computers where it accesses sensitive data on Stargate program and its personnel. The virus program is detected and apparently deleted from the mainframe. Unknown to all however the entity's program has downloaded itself into the MALP (Mobile Analytic Laboratory Probe) room where it continues to thrive building itself a new body in order to contain the immense volume of data it has purloined. When SG-1 discovers the entity Col. Jack O'Neill wants to destroy it but Maj. Samantha Carter and Dr. Daniel Jackson feel that they should attempt to communicate with it first. Carter tries — only to be overcome by a blast of energy. She is rushed to safety while O'Neill shuts down the entity presumably killing it for good this time. However the rest of SG-1 soon learns that the entity is far from dead. In fact it now exists in a new vessel one capable of storing even greater volumes of data: Carter's body. With the base under siege and the alien entity poised to overwhelm them all O'Neill and company are confronted with a dire prospect: In order to save Stargate Command they might have to sacrifice one of their own.