The Infiltration into the Overkill Facility was a successful mission undertaken by S.H.I.E.L.D. to obtain a dangerous weapon capable of disrupting all weapons systems across the world and activating nuclear weapons.
S.H.I.E.L.D. learned of the location of the Overkill Device, and agent Victoria Hand gathered Phil Coulson's team to the Hub to discuss a plan to retrieve the weapon from the hands of the South Ossetian rebels holding it, as they would likely use the weapon to bring destruction to the United States of America. Hand recommended a small team consisting of Grant Ward and Leo Fitz, as Ward had contacts in Siberia and Fitz could disarm the weapon.
Unbeknownst to Phil Coulson and his entire team, Victoria Hand had made the decision to not send a rescue team to extract Grant Ward and Leo Fitz once the mission was complete, instead planning on leaving them behind to escape by themselves once the Overkill Device had been disarmed. Hand defended this decision by noting that Natasha Romanoff and Clint Barton never went into a mission with an escape plan.
- "Are you familiar with the term slam and cram?"
"No and I don't think I want to be."
"How attached are you to your pinky?"
"Very, very attached, and before you ask another terrifyingly vague question, let me be clear. Any plan that involves even one of those scenarios isn't going to work for me."
- ―Grant Ward and Leo Fitz
Grant Ward and Leo Fitz accepted the mission and arrived in Siberia, where they tried to meet with Ward's contacts. They soon learned that Ward's contact had been killed and they were captured by local mobsters led by Marta. Fortunately, Fitz's quick thinking won them Marta's favour and they were able to make their way to the facility where the Overkill Device was being held. As the pair prepared to sleep before the mission went underway, Ward forcibly taught Fitz that it was unacceptable to bring a freshly made sandwich on such a dangerous mission as dogs would be out hunting them.
The next morning, the pair broke into the facility and hunted for the Overkill Device. Before long, Ward learned that Victoria Hand was not sending in a back-up team to bring them out, but continued the mission regardless. Once they had found the device, Fitz began disarming it until Ward informed him that there would be no rescue team. Instead of running for safety, Fitz continued with the mission and disarmed the weapon. The South Ossetian rebels then arrived and attacked, while Grant Ward fought them, Leo Fitz used the Overkill Device to destroy their weapons until Ward could defeat them.
With the attacking rebels defeated by Grant Ward, the pair ran outside with the Overkill Device, but were soon surrounded by the rest of the rebels who held them at gunpoint. Both Ward and Fitz accepted that they were about to be captured and tortured to death for their actions, but before they could be caught, Melinda May arrived, piloting the Bus, and rescued the pair, knocking back the rebels with the Bus' engines and allowing them to enter. While they were on the mission, Skye had informed Phil Coulson of Victoria Hand's lies and he had put together his own rescue team to save his team members.
- "I didn't solve this today."
- ―Leo Fitz
The Overkill Device was put under S.H.I.E.L.D.'s protection while Phil Coulson reunited his team mates. Although her orders had been disobeyed, Victoria Hand accepted Coulson's actions as she noted that Coulson's Team did not need an escape plan as they would deal with it themselves. Leo Fitz returned to the Bus but decided not to inform Jemma Simmons that the sandwich she had made him had been wasted; she, however, informed him that she had shot agent Jasper Sitwell with an I.C.E.R. while he had been away.
Later, Fitz, having suffered brain damage, found it hard to express that the Overkill Device would be the appropriate weapon to use against Carl Creel. Alphonso Mackenzie, Fitz's new close male friend, was able to decipher Fitz's thoughts.