ENT Season 1, Episode 3 Fight or Flight

Plot

It is May 2151, and the crew of Enterprise are settling in, and are slowly getting acquainted with one another. The crew is restless as they have not encountered anything new in the past two weeks: Captain Archer is trying to locate a squeak in his ready room and anxious that they have not discovered any worthwhile planets yet; Sub-Commander T'Pol points out that Vulcans don't select their destination by what piques their interest as they don't share humanity's enthusiasm for exploration; Lieutenant Reed and Ensign Mayweather are running weapons simulations which are slightly off; and in Sickbay, Ensign Sato cares for a slug brought back from an away mission.
When T'Pol picks up a drifting Axanar vessel on sensors, Enterprise drops out of warp to investigate. The ship shows evidence of weapons fire and bio-signs but does not respond to hails. Archer is eager to make first contact with a new race, but T'Pol recommends non-interference. After discovering multiple hull breaches, an away team in EV suits is dispatched. The alien crew is soon found dead, suspended upside-down with tubes attached to their chests. Spooked, the away team retreat and Enterprise departs. Doctor Phlox and Sato discuss her fears over the incident, and draw parallels between her and the slug being out of their natural environment.
Eventually, Archer decides to return to the ship. Phlox discovers the bodies are being harvested for a chemical similar to lymphatic fluid, whilst Commander Tucker restores communications and Sato decodes the Axanar language.[6] When T'Pol warns Archer that a ship is approaching, the crew withdraws to Enterprise, but not before shooting the harvest pump. The alien vessel attacks, but Enterprise cannot return fire accurately due to problems with the targeting scanners. A second Axanar vessel arrives, and Sato persuades them that the alien ship was responsible. They then attack the hostile ship and Enterprise is saved. The episode ends with Sato and Phlox releasing the slug on a new planet.