Tellek

Tellek was the alias for a Romulan spy and agent of the Tal Shiar who posed as a Vulcan Starfleet operations officer aboard the USS Ellesmere (NCC-21464) in the mid-24th century. In 2339, he sabotaged the Ellesmere's navigational array, causing it to cross into the Romulan Neutral Zone, where it was fired upon and disabled by a Romulan warbird.

This sabotage was part of a plan to steal Starfleet sensor and deployment data and return it to the Romulan Star Empire. However, the Ellesmere captain, Laura Blake, was able to encrypt the computer before Tellek could recover the data, though Tellek killed her in a confrontation shortly afterward. Tellek attempted to maintain his cover long enough to decrypt the computer data and attempt escape, but the escape was foiled by the crew of the USS Tempest (NCC-10535), which had responded to the Ellesmere's distress call and discovered the sabotage in the course of rendering assistance.

The Tempest was ultimately able to apprehend Tellek after he acquired the sensor data but before he could return to Romulan forces.

Current Status
Following the Ellesmere's safe return to Federation space, Tellek was handed over to Starfleet Security, where he continues to be detained and interrogated.