Ep 17. Enigma

Enigma is the seventeenth episode of the first season of Stargate SG1. The episode starts with SG1 returning from a mission on an uninhabited planet. As they are heading back to Earth, they receive a distress signal from a planet named Tollan. The team, along with Dr. Jackson, head to Tollan to investigate.

Upon their arrival, they meet with the Tollans, an advanced race that has managed to develop weapons that are more powerful than anything the team has seen before. The Tollans are reluctant to give SG1 any information and seem to be uninterested in making friends. However, SG1 discover that the Tolans have a Stargate and have been in contact with Earth for some time.

During their stay in Tollan, SG1 is informed that there is a spy within their ranks. They soon discover that the spy is a sharp young woman named Linea, who had initially been exiled by Tollan after being the sole survivor of a terrible experiment. Linea had subsequently been rescued by the Asgard and had set her sights on Earth.

SG1 is tasked with keeping Linea occupied while they investigate the true nature of her intentions and the extent of her abilities. Linea, who is a gifted scientist, begins to win the trust of some of the team members. She slowly starts to reveal her true nature, and with every passing moment, SG1 becomes more apprehensive of her intentions.

With the help of the team, Linea manages to make her way through the security measures in the Tollan's city. She activates a device that releases a deadly virus that threatens to destroy the city and everyone within. SG1 must race against time to stop the virus before it kills everyone.

Despite their efforts, the team is not able to stop the virus in time, and it devastates the city, killing many of the Tollan inhabitants. SG1, along with the Tollans, investigate the incident and discover that Linea had intended to destroy the Tollan for their arrogance and for exiling her to her imminent death.

The episode ends with SG1 departing Tollan, with Daniel Jackson reflecting on the violent nature of humanity and how it might impact other civilizations. Overall, Enigma is an exciting episode that explores humanity's capacity for evil and the consequences of our actions. With a well-scripted storyline, top-notch acting, and excellent visual effects, this episode is a must-see for Stargate SG1 fans.