Trama

Commander Riker's inability to fall asleep begins to show in other members of the crew in other forms, putting the Enterprise on the trail of a mystery.

Commander Riker has not been sleeping well but Dr. Crusher can't find anything wrong with him. He is constantly exhausted and has images of objects in his mind that he can't quite place. He is not the only one with a sense of deja vu and with others, manages to piece together what has been happening. It would seem they are being taken from the ship during their sleeping hours by a race conducting experiments on them. Who they are and what they hope to achieve is unknown but everyone agrees it must be related to the inter-dimensional hole in space that is somehow being created in one of the cargo bays.—garykmcd

Commander Riker has not been sleeping well but Dr. Crusher can't find anything wrong with him. He is constantly exhausted and has images of objects in his mind that he can't quite place. The Enterprise is charting a huge nebula. Geordi and Data have devised a plan to use warp energy to speed up the process, by channeling it through the EPS processors in the cargo bay. Shortly thereafter the ship's sensors notice an explosion in the EPS processors of the Cargo Bay. But a physical check of the bay reveals no explosion and nothing out of the ordinary.

Riker is not the only one with a sense of Déjà vu. Geordi and Data also start having "gaps" during their waking hours where they seem to have no memory of recent time that has elapsed. With others, they manage to piece together what has been happening. Geordi, Worf and Riker all have memories of being in a dark room with an inclined metallic table. They piece together that the table had a chest restraint, a bright light shining into their eyes and a scissor like instrument held close to their face. The dark room had fast clicking noises in the background. All of a sudden, Data and Geordi notice a spatially inverted Tetryon particle beam emanating from the EPS panel in the cargo bay. Tetryon particles are unstable in normal space, and thus should not exist in physical form. Geordi and Data can't explain it.

Beverly finds that the trio has been exposed to a Neuro sedative and have been exposed to Tetryon rays. Riker's arm has been amputated and surgically re-attached. It would seem they are being taken from the ship during their sleeping hours by a race conducting experiments on them. Who they are and what they hope to achieve is unknown, but everyone agrees it must be related to the inter-dimensional hole in space that is somehow being created in one of the cargo bays. The Tetryon rays are now focusing on a single plane in the cargo bay and starting to form into a portal.

There is no way to stop the expansion of the portal. In a few hours, it will breach the hull. Picard theorizes that the subspace sensor arrays juiced up by warp power triggered something in another dimension/Universe who started using the Tetryon rays to create a portal into this universe. Graviton waves can close the rupture, but they have to do this at the source of the Tetryon rays.

Worf suggests creating a homing signal device and keep it with Riker, as the aliens have taken Riker with them every single night without fail. With the homing device, the location/dimension of the other universe can be tracked. When Riker is returned, Geordi plans to use Graviton waves to neutralize the Tetryon waves and close the portal. Beverly offers to give Riker a neural stimulant, to ward off the neural sedative administered by the aliens

Sure enough, that night Riker is taken away by the aliens. A portal opens right into Riker's room and sucks him into it, while he lay in his bed. But this time Riker is awake. Geordi locates Riker's signal from the homing beacon. Geordi hits the location in time space with Graviton beams, forcing the rupture to close. Riker manages to escape before the portal closes completely. The crew speculates that the aliens were explores themselves, like the Enterprise. They were Solagen based life forms and couldn't exist in our Universe. They created a lab in their universe where humans could survive and the portal was to create an environment in this universe, where they could survive and communicate. Riker says they were not all peaceful.