Seventeen Seconds

The Shrike attacks the Titan, injuring Shaw who transfers command to Riker. Beverly says she did not tell Picard about Jack to keep their son safe from his enemies. Riker attempts to escape the nebula but they are cornered by the Shrike using portal technology. Picard advises Riker to lure the Shrike into a trap, but Riker wants to flee and prioritize saving the crew. Jack and Seven deduce that Vadic is tracking a gas leak on the Titan and find an ensign sabotaging the ship. He is revealed to be a Changeling and escapes their custody. Using the freighter La Sirena, Raffi and Worf capture a criminal that they believe is responsible for the attack on M'talas Prime. They discover that he is also a Changeling, part of a group that has been fighting the Federation since the end of the Dominion War, and realize that the attack was just a distraction.

Summary from Wikipedia, CC BY-SA 4.0.