In 2370, Sirol discovered a fragment of the experimental USS Pegasus in the Devolin system, and was assigned to find the rest of the ship in the system's asteroid field. When the USS Enterprise-D arrived on the same mission two days later, Sirol claimed he was conducting a survey of gaseous anomalies.
After the Enterprise-D entered a large asteroid where the Pegasus had settled, Sirol fired on the asteroid and sealed them inside, claiming the Romulans were conducting "geological experiments". Sirol offered to transport the Enterprise-D crew out and return them to the Federation after a "short stay" on Romulus, but the Enterprise-D escaped on its own by means of an illegal phasing cloaking device that had been tested on the Pegasus. The Enterprise-D decloaked in front of Sirol, and informed him that the Romulan government would be contacted shortly concerning the incident. (TNG: "The Pegasus")