The episode begins with Captain Archer in his ready room trying, unsuccessfully, to get to know Lieutenant Reed better. Meanwhile, Enterprise nears an uncharted and seemingly uninhabited planet for closer observation. Its proximity, however, triggers a cloakedmine, heavily damaging the ship and flooding Sickbay with injured crew members. Soon, another cloaked mine is detected as it attaches itself to the hull, but it doesn't immediately detonate for some reason. With the core already damaged, it is feared that a further detonation will totally disable the vessel. Reed then goes EV to try to disarm it. As a backup plan, Archer orders Commander Tucker to prepare to detach and jettison the affected section of hull plating.
Initially Reed's efforts seem to be working, but an alien vessel suddenly decloaks, and fires warning shots at the ship. Ensign Mayweather assumes manual control and steers the ship carefully out of the minefield. During the maneuvers, however, a jolt accidentally activates another magnetic grappling arm that impales Reed's leg before attaching itself to the spaceship's hull, thus pinning him down. Archer also dons an EVA suit and attempts to disarm the mine under Reed's direction.
Enterprise then makes first contact with the Romulan Star Empire when two Warbirds decloak and demand that they jettison the mine with Reed attached. Knowing that any attempt to cut the arm would set off the mine, Reed becomes insistent on sacrificing himself to save Enterprise. Archer returns to the ship and requests two shuttle hatches from a puzzled Commander Tucker, also ordering him to detach the hull plate as planned. As the plates and the attached mine float off, he severs the spike holding Reed. This arms the mine, but Reed and Archer are also able to shield themselves from the resulting explosion. Enterprise then collects the crewmen before warping away from the secretive Romulans.