The Enterprise encounters an unknown alien vessel that quickly scans the ship and begins penetrating into the computer, before the crew can take defensive action a beam scans across the ship, wiping out everyone's memories and damaging the memory banks of the computer.
The crew begins to try and to figure who they are, among them a "new crew member" in the form of Commander MacDuff, and while they don't have any memories of who they are, who anyone else is, or of their mission they do retain the memories and skills of their profession.
After some time they're able to recover some computer data that gains them their names and ranks and the ship's mission. They find out they're in the middle of a covert operation to eliminate the command center of an alien race they've been at war with for years. It's a covert operation in which they're to maintain radio silence in order to end the war.
Some of the crew are skeptical of this mission but they chose to go forward with it anyway and work on regaining their memories and computer data along the way. Attempts to recover either are unsuccessful. When they encounter the perimeter of the alien space they find out they outmatch the aliens by orders of magnitude but Commander MacDuff convinces them to charge forward and even enlists Worf to back him should Picard's reluctance prove to be a danger further along.
Once near their target the alien defenses continue to pose no threat and they find out the command center poses no threat whatsoever, a single photon torpedo will destroy the base containing 15,000 lives. Picard decides to not fire on the base and tries to open a channel, at this point MacDuff, as First Officer, takes command and tries to order Worf into firing but Worf refuses. MacDuff tries to fire the weapons himself but is killed by Worf and Riker.
Picard learns from the aliens they were about to attack that they were at war with another race, MacDuff's race, and that MacDuff's race used a memory-blocking technology on the ship in order to use it win the war. Crusher and Geordi work to restore the memories of the crew and the damage to the ship.
During all of this the blanked Riker and Ro find themselves in a more romantic relationship, one Troi believes occurred due to their subconscious desires during their memory loss.
In order for this episode to work we have to accept the fact that an alien race that is 100 years behind the Federation in weapons and defensive technology is able to impact the memories of the crew (including numerous different species) alter and damage the ship's data banks (more complicated alien technology) and even damage Data (a unique creation.) It's a pretty big cookie to chew but we need to eat it in order for the themes and idea of the episode to work.
And that seems to be more focused on who are characters "really are" and allow them to act on their impulse and intuition unfettered by memory.
One of the bigger ones occurs between Worf and Picard as the crew initially tries to figure out the command structure of the ship. Worf's Klingon, warrior, instincts pretty much allow him to pull out ahead of everyone else and pretty much assume command (even though when he "came to" he was behind the tactical console and Picard was in the captain's chair) and prepare the ship to continue it's mission in the "war" and be ready for battle. But, in the end, his duty to the captain and perhaps his sense of "good" or even a Klingon sense of a "fair fight" comes out at the end when he realizes the aliens the ship is set to destroy poses no threat and Picard decides not to fire.
Picard's diplomacy skills come out during all of this even to the extent he's willing to not rock the boat more than need-be and defer command to Worf and instead offers suggestions until the manifest is discovered.
Troi's emotions towards Riker are strong in her during the events as is her intuition that what is happening isn't right. It's nice and sweet to see her loving emotions for Riker come out to play more than they usually are when we see the two interact in a more professional manner on the ship.
But, probably greatest of all, is the aggressive sexual tensions between Riker and Ro are broken down and the two consummate their relationship. At least twice.
On a first viewing it's obvious MacDuff is up to no good since he literally appears out of nowhere, on repeat viewings this some what annoying as it's just so obvious MacDuff is up to no good and it a good question on what the episode would have been like if MacDuff had been a character in the series for a while only to come out to be an impostor the entire time. But that's probably not an entirely realistic idea especially given the episodic nature of the show.
So, accepting that MacDuff is up to no good it's a bit of tension to know what his motives are and what is really happening, even though everything we're told and discovered as the episode goes on. I did get a laugh after the procedure to try and restore his memory goes awry in sickbay and MacDuff turns to the camera, breaks the fourth-wall, and twirls his mustache and laughs sinisterly.
On a slight nitpicking front, the order of the crew the computer gives us when reciting the manifest is sort-of odd. It gives the command officers (Picard, "MacDuff", Riker) first and after that seems to make some odd choice on how to put people up there and it doesn't seem to align with either rank or where everyone lies in the command structure of the ship. It's also pretty odd the helm officer, Ro, is in there unless she's the chief... helm officer?
The base for the aliens is a reuse of the Edo "god" from way back in the first season.
There's some pretty nice-looking effects shots in the episode, particularly as the ship makes its way through the aliens' perimeter, inner defenses and approaches the command center.
In the end, a good episode.
yeah, I guess those are good points. It's hard to defend this episode. lol I still don't mind it that much
. Kind of like Voyager's Friendship One, except the aliens figured out how to work it and used it on the crew of the Enterprise to win their war.
