“Power Play” is episode fifteen of season five of Star Trek: The Next Generation.
The Enterprise is in orbit about an unexplored M class moon of Mab-Bu VI. It’s reported as being uninhabited but a weak distress call was picked up. There are no signs of life and the location of the signal cannot be determined, but electromagnetic interfere in the atmosphere is interfering with sensors. Data has heard something similar at Starfleet Academy; the signal matches the distress call of a Daedalus class starship, which have been out of service for 172 years. 200 years ago, the USS Essex commanded by Captain Bryce Shumar disappeared in the area; the signal matches that of the Essex. The captain is saying it’s not worth checking any further, but Troi can detect something alive on the moon.
The interference makes it too dangerous to use transporters, so Riker, Troi and Data head down in a shuttle. This proves no safer and they crash. On the Enterprise, Ensign Ro reports the shuttle has crashed. Worf cannot get a position, but Ro followed it almost the whole way down.
Riker was injured in the crash, with a broken arm. Communications don’t work and Riker doesn’t think there’s anything alive and there’s a storm coming. Data detects no other lifeforms but Troi can sense life, coming with the storm.
Geordi is with O’Brien in the transporter room. The chief suggests beaming down with a pattern enhancer. It’s dangerous, but he thinks he can do it. The captain checks he’s aware of the risks and O’Brien beams down. He finds the others by the shuttle and they start putting up the pattern enhancers. O’Brien is placing the final one when a bolt strikes it and knocks all four down. Glowing balls of energy appear and enter Troi, Data and O’Brien. Riker staggers up and activates the last enhancer and they beam out.
In sickbay, the doctor tells the captain that Riker had the worst of it. All head to the bridge and Troi wants a word with the captain privately. On the bridge, Riker orders a search pattern near the crash. Data suggests one near the southern pole but Riker disagrees. Troi is talking to the captain in his ready room; she, too, suggests the south pole. On the bridge, Ro is locked out and the orbit has changed. Data knocks Riker down and O’Brien does the same with Worf. Ro shoots him but to no effect. Riker transfers command to engineering and Data hits his console in a rage. Troi knocks down the captain.
The effort to take the bridge having failed, the three leave in a turbolift. Riker gets bridge controls back, and tells the captain what happened. Despite attempts to trap them in the turbolift, they’ve got out when Worf and a security team arrive. Data is able to use ‘his’ entity’s substructure to get past security forcefields and they head to Ten Forward. Worf and his team arrive, but their phasors have no effect; Troi is stunning everyone.
It’s not possible to shut down Ten Forward’s consoles without taking down the entire saucer section. Not-O’Brien puts the transporters into diagnostic mode. Not-Data isolates the room. Captain Picard wants Dr Crusher to see if anything can explain this from the biofilter readouts from the transporter. When Not-Troi is contacted, she tells the captain to move the ship to polar orbit, or people start to need medical attention. They do, but slowly.
Dr Crusher reports unusual synaptic activity in the three; it might be another lifeform in them. Riker may not have been affected because of his broken arm. Pain might drive the entities out of the three; a plasma shock would even affect Data. They can then contain the energy after it comes out.
Captain Picard offers himself as a hostage in exchange for his injured crew. The three have the knowledge of their hosts it seems, but they are clearly someone else. The captain is rather dubious of who they claim to be. Somehow, they need to overpower all three, when they have hostages.