Eager to raise the morale of the crew, Janeway jumps at the chance to explore a nebula emitting a high level of omicron particles, which might prove useful for the ship's energy reserves. But shortly after Voyager enters the cloud-like formation, it encounters an energy barrier that brings the ship to a dead stop. Breaking through, the ship continues its penetration of the nebula's inner reaches, only to be bombarded by peculiar globules that attach themselves to the hull. With the globules beginning to drain the starship's energy reserves, Janeway orders the crew to leave the nebula, but this time they can't get past the energy barrier until they blast their way out with a photon torpedo.
The excitement over, Paris invites Kim to tag along for some rest and recreation in Sandrine's, a holodeck recreation of a French bar that Paris frequented in his Academy days. In the meantime, Torres spends her time analyzing one of the globules that attached itself to the hull. Surprised at the results, she confirms her findings with the Doctor and then notifies the Captain.
The globules are organic elements of a much larger lifeform, she explains. In other words, the nebula was actually a living entity and the phenomena they encountered were part of the entity's natural defense systems. Concerned that the encounter with Voyager may have caused the lifeform serious injury, Janeway proposes returning and repairing the harm they've done. The Doctor tells her that the organic samples seem to indicate that the lifeform has the capacity to regenerate, given the appropriate stimulation.
Returning to the "nebula," Voyager re-enters and prepares to irradiate the wound with a nucleonic beam. But they're interrupted when the lifeform's natural defense systems again attack the ship, forcing them away from the wound. Although the ship sustains damage, they are eventually able to return to the injury site. The Doctor suggests a method of "suturing" the wound, which they manage to do after distracting the entity's defense systems with a microprobe. Just before the wound seals over, Voyager escapes from the cloud and sets course for a planet where they can replenish their depleted energy reserves. En route, Janeway joins Paris and her other senior staff officers at Sandrine's, where everyone is surprised with her pool playing expertise.