As the Prometheus returned home from Tagrea, it was required to make regularly scheduled stops to allow the temporary hyperdrive engines to cool down. During one such stop, approximately 250 light years from Earth, the ship would encounter a unique gas cloud formation similar to a nebula, although it appeared to be made up of a denser group of gases than that of a typical nebula or gas giant. Carter had hoped to study the formation, however, as the Prometheus dropped out of hyperspace, it came under attack from an unknown alien vessel and was forced to take cover within the gas cloud.
Carter sustained a head injury during the attack and awoke to find that the ship's crew had vanished. Both the Prometheus and the alien vessel were stranded within the cloud formation, the cloud's composition prevented the activation of a stable hyperspace window, the sub-light engines could not be engaged, weapons and shields were ineffective, and the corrosive gases of the cloud threatened to breach the hull within hours. As Carter struggled to remain conscious and to find a way to escape from the cloud, she was visited by the people in her life who appeared to her as figments of her own mind and offered her messages of guidance and support. Among them was an enigmatic young girl named Grace who appealed to her inner child, and provided her with a solution.
By engaging minimal power to the hyperdrive emitter, Carter was able to cause a partial shift into hyperspace, essentially taking the ship out the cloud's space-time long enough to eliminate its effects on the sub-light engines. No longer affected by the cloud's corrosive gases, the sub-light engines could be engaged. Carter bargained with the alien ship, offering to expand the hyperspace bubble to encompass the alien vessel as well and to give them a means of escape in exchange for the return of the Prometheus crew. Instantly the crew materialized on board, with no memory of the incident. Carter engaged the sub-light engines, successfully extracting both ships from the cloud formation, and the alien vessel retreated.
Cross Reference: Samantha Carter, Erin Gant, Grace, Hyperspace, Prometheus, William Ronson
Episode Reference: Grace