The Enterprise is in the Beta Renna(?) system, picking up delegates from two opposing planet, who both want to join the Federation. Then Data detects an oncoming storm, traveling at warp. They scan the storm a bit, and then Work gets zapped by funky blue lightning.
Wait, why's he been moved into the corridor before Crusher arrives? Crusher gets zapped by the lightning while treating Worf, and acts oddly when Troi talks to her. Then she goes an has a surreal conversation with Wesley before heading up to the bridge and zapping the lightning into helm control. Malfunctions begin occurring across the ship.
In the B plot, the delegates are acting a bit ornery. Riker tells them off a bit.
The Enterprise drops out of warp, causing Picard to call another meeting, during which it's established that there's a saboteur on board. There's a brief discussion about Sherlock Holmes, during which you can practically see the cogs turning in Data's head.
In engineering the lightning zaps engineer Singh, killing him. Later on, Work, Geordi and Wesley discover the warp engines have been mysteriously fixed, and the ship goes back into warp. Yar questions the delegates a bit and doesn't get anything useful. She talks to Riker and Data, who is now emulating Sherlock Holmes.
Troi hypnotizes Crusher and establishes that she was being mind-controlled before. There's yet another meeting, then Geordi loses helm control, and the lightning zaps Picard, taking him over (OH NOES!)
Picard orders the ship turned around and the rest of the bridge crew start questioning him. O'Brien tries to get the delegates back into their quarters with little success.
The bridge officers discuss relieving Picard of duty, but can't think of just cause. Riker and Crusher confront him without much success, and Riker is later ambushed by a group of delegates who are playing hide and seek. Crusher talks to Picard again, and establishes there's more than one person in there.
The Enterprise reaches the cloud, and Picard launches into a spiel about the alien's life story. He intended to beam himself into the cloud as a combined energy being. Crusher attempts to relieve him of duty, but he zaps the bridge officers and sods off to the transporter room and beams out.
An hour later, Riker opts to return to their previous course, but then Troi says she can detect Picard. They nudge the ship into the cloud a bit, and Picard hops into the ship's circuitry. Data uses the Captains pattern in the transporter buffers to rematerialise him. You can do that? Picard appears confused. Yar turns up and says that a member of one of the delegations may have been killed by the other delegates, as a sort of way of resolving the B plot. Teh end.