(the story takes place in just a couple of hours before Reapers attack Earth)

Gabriella Daniels and Kenneth Donnelly, former Cerberus engineers who were rescued by Shepard from the Collectors' grasp and survived the suicide mission, are doing their part to help the Alliance. Although they were being held and monitored on the Citadel, the two were very knowledgeable in engineering and at times were escorted by guards to an isolated Alliance base located in Artemis Tau Cluster, known to have many Prothean ruins and other rare materials from its asteroid belts. There, they were invited to build new engine tech and were partially involved in N7 weapons research under Lieutenant D. Eugene from the Alliance Engineering Corp. While weapon development was not their field of expertise, the two were eager and ready to help — always working hard to do what they could to help Shepard.

Gabriella and Kenneth heard about some kind of big disturbance in another system nearby a few hours earlier, but neither one knew what was going on exactly. It was also around this time that they realised they were being escorted by a new guard: a mysterious looking lady with stylish armor – very different to what any of the other Alliance soldiers wore. Kenneth took notice and asked Gabriella:
"Gaby, don't you want to wear those black heels that our new guard lady's wearing? They pair so nicely with her sleek black and white armor."
She replied: "Kenneth, you are such a dog... And you'd better watch out, she has a sword."

That night, the two of them ended up staying overtime to finish their work at the factory. Their hard work paid off: the newly made Black Widow and N7 Valiant sniper rifles were ready.

Suddenly, Gabriella heard loud noises coming from the exit; it was strange since no one else except the guards were supposed to be there. Gabriella went to investigate, only to find out that someone had killed all the remaining guards who had deep lacerations on their bodies. She turned, only to see a dark figure approaching her with a sword. It was then that Gabriella recognised her, it was their new guard who turned out to be Cerberus' sleeper agent, a Phantom, and she was here to acquire the new tech blueprints from the Alliance Engineering teams.

Gabriella quickly ran to Kenneth to warn him. As engineers, they had no weapons to defend themselves with. Furthermore, as detainees, their tech powers were limited by the Alliance, which meant they were left with the two Drones that they used for repairs. They had the sense to hack their drones to make them combat ready, but Gabriella and Kenneth now had to rely on the two new sniper rifles they worked on to get out of here alive.

The Cerberus Phantom has called for reinforcements to seize the factory. As more troopers file in, the two engineers must now remember the Alliance combat training that they undertook a couple of years ago to protect the Alliance's blueprints and fight their way out.