The helmet carries an alien virus transmitted through static electricity. Tragically, during the investigation, Jemma Simmons realizes she has been infected. A Race Against the Clock

The tension shifts to the "Bus" (the team's plane), which becomes a high-altitude quarantine zone. Simmons estimates she has only before the virus causes her to erupt in a lethal electrostatic burst—one strong enough to take down the entire plane.

The story begins with a series of bizarre deaths: victims are found hovering in mid-air, surrounded by crackling electrostatic energy, before their bodies internally combust. Investigating a scout campsite and a local firehouse, Fitz and Simmons trace the cause back to a —a "souvenir" kept by firefighters who served during the Battle of New York.