In "Cause and Effect", the Enterprise becomes trapped in a time loop. This was the 117th episode of Star Trek: The Next Generation, and the seventeenth episode of TNG's fifth season. "Cause and Effect" premiered on the week of March 23rd, 1992. The episode was written by Brannon Braga and was the fourth episode directed by Jonathan Frakes.


Captain's log, stardate 45652.1 
The Enterprise has entered an area of space known as the Typhon Expanse. We are the first Starfleet vessel to chart this unexplored region.

While exploring the Typhon Expanse, the USS Enterprise-D is caught in a temporal displacement loop in which they are repeatedly destroyed while colliding with another starship, the USS Bozeman (NCC-1941).

After each collision and reset of space and time, the crew starts to have déjà vu and are able to predict a few events as they occur. Among those who experience the déjà vu is Doctor Beverly Crusher, who at first is able to call Commander William Riker's bluff in a game of poker. After the Enterprise is destroyed multiple times, Dr. Crusher attempts to deviate from the actions she knows she is about to perform. Among those actions is scanning Geordi La Forge and administering a hypospray for symptoms of an ear infection and dizziness. Beverly was going to run the standard tests but somehow had a feeling that they would turn out negative, so she ran an optical diagnostic which traced the problem to Geordi's VISOR. It turned out that his dizziness was caused by a phase shift in his visual receptors, which caused him to see images that were not there, described as "blurry afterimages". Beverly then ran a scan to see if she could detect what he was seeing and picked up minuscule distortions in the surrounding dekyon field. Somehow his VISOR was picking up those distortions and transmitting them as images.

Other symptoms that Beverly observes is that right before going to bed she starts to hear voices which was related to a dekyon field distortion that was detected at the same time. After sorting through all the distortion, Data and Geordi are able to clear up a recording of the voices Crusher heard. During a meeting with the senior staff they play one recording in which Captain Jean-Luc Picard is clearly heard ordering that all hands abandon ship. At this point the crew discover that they are caught in a time loop. During the meeting it is proposed that they try and attempt to send a deliberate echo using a dekyon emission into the next time loop to attempt to prevent the ship from being destroyed again, the only down fall was that the message would only be a few characters in length or a single word. To accomplish this, Data would modulate the dekyon emission to detectable only by him.

During the next loop, Data receives the message and is startled that everything he does comes up with the number three or in multiples of three. Leading up to the Enterprise's destruction, Data is able to interpret the message he received, the number three, to mean the number of rank insignia on Commander Riker's uniform. To that effect, Data implements Riker's plan, to vent the main shuttlebay to move the Enterprise from a collision course. The plan works. Afterwards, the Enterprise makes contact with the other ship, it is the Bozeman, commanded by Morgan Bateson. The ship was presumed lost with all hands nearly 80 years before.



Claudia AlisovMorgan BatesonLloyd BoenBeverly CrusherDataJaeGeordi La ForgeMartinezNelsonAlyssa OgawaJean-Luc PicardWilliam T. RikerRo LarenDennis RussellDeanna TroiParvana WhitcombWorf, son of Moghunnamed USS Bozeman personnelunnamed USS Enterprise (NCC-1701-D) personnel

Starships and vehiclesEdit

USS Enterprise-D (Galaxy-class explorer) • USS Bozeman (Soyuz-class cutter) • BermanPiller (type-6 shuttlecraft)


Shipboard locationsEdit

USS Bozeman (NCC-1941) 
USS Enterprise (NCC-1701-D) 
bridgeengineeringobservation loungequarters (Riker's, Crusher's) • ready roommain shuttlebaysickbay

Outposts and stationsEdit

Starbase 12

Stellar regionsEdit

the galaxy (Typhon Expanse)

Races and culturesEdit


States and organizationsEdit

Federation (Starfleet)

Technology and weaponsEdit

Soong-type androidcommunicatorshuttlecraftstarshiptractor beamwarp drivewarp nacellewarp corewarp core ejection systemintercomimpulse enginemaneuvering thrusterVISORtricorderpositronic brainpositronic subprocessordekyon emittertimebase beaconchronometerpositronic netescape pod

Ranks and titlesEdit

Federation Starfleet ranks (2270s-2350s)Federation Starfleet ranks (2360s-2370s)captaincommanderlieutenant commanderlieutenantlieutenant junior gradeensigncommanding officerfirst officerchief medical officercounselorsecurity chiefchief engineerengineerdoctornurseflight controlleroperations managersecond officerofficerqueen

Other referencesEdit

Klingon language (nIb'poH) • ranktitleinsigniarank insigniauniformStarfleet uniformStarfleet uniform (2366-2373)Starfleet uniform (2278-2350s)technologyspacetimetime-travelsenior staffwarp plasmaplasmalog entrybeveragecaptain's logstardatestarbasegalaxypokerplaying cardearvertazineplantlifeformhumanoidspace-timetemporal distortionexplosive decompressionmedical logdekyonoptical diagnosticred alertdayyearhourmedicineheadachecommon coldtemporal causality loopbrainnervous systemoptic nervedéjà vu


The Bozeman departs Starbase 12, three weeks before becoming ensnared in a temporal distortion. (Bateson describes the year and number of weeks since their departure)
The Enterprise-D starts to experience repetitions of time. After over 17 days of repetition, they break the cycle by avoiding collision with the Bozeman. (Worf determined that it had taken 17.4 days for the crew to perceive the loop and free themselves, even though only a few hours had passed)


Related worksEdit



published order
Previous episode:
The Outcast
TNG episode produced Next episode:
The First Duty
Previous episode:
The Outcast
TNG episode aired Next episode:
The First Duty
chronological order
Previous Adventure:
A Stitch in Time
Part 2, Chapter 20
Pocket Next Adventure:
Ship of the Line
Chapters 6-7

External linkEdit