The Mandalore Plot
Though he appeared to be loyal to her, he really worked for the Death Watch, acting as a double agent. Merrik appeared to be a calm and soft-hearted man, and used these qualities to throw people off. Tal was on the Coronet with the Council of Neutral Systems, Obi-Wan Kenobi, Anakin Skywalker, and Duchess Satine as they traveled to Coruscant to plead its case of neutrality before the Senate. Pre Viszla working with Count Dooku, planned to have Satine eliminated. Merrik managed to smuggle a box of assassin probes onto the ship, and secretly activated them.
When all the assassin probes and the probe killers which were in them were supposedly destroyed, Kenobi and Skywalker discovered a senate stamp which allowed the box to be brought onto the hold. The two Jedi knew one of the senators was a traitor. Kenobi and Skywalker found a surviving assassin probe, cased it, and brought it to the dinner table with the senators. Realizing that the probe would not attempt to kill the individual who had it was programmed to work for, the person who had allowed the probes on to the ship, it became clear that Merrik was the guilty party based on the probe not trying to kill him. They all realized that Merrik was a traitor.
In the confusion following, Merrik knocked the case down, releasing the probe. While it started to attack all the senators, he took the opportunity to take Satine hostage. He killed the pilots, and contacted Vizsla, informing him of his success.