“Yesterday’s Enterprise” was a third season episode written by: teleplay—Ira Steven Behr,Richard Manning,Hans Beimler,Ronald D. Moore and based on the story by Trent Christopher Ganino and Eric A. Stillwell.
The Enterprise is monitoring an anomaly in space—-some sort of time distortion. Then out of this area of space, the Enterprise C class emerges. Then we see the Enterprise D crew transform into different looking uniforms and the bridge of the ship is more dark and less spacious. Chief of Security Worf has been replaced by Tasha Yar, the crew’s first security chief.
Captain Picard hails the other Enterprise and that crew slowly learns they have traveled in time—22 years into the future. They were responding to a distress call on a Klingon outpost when they were attacked by Romulans and then entered the rift.
Meanwhile, Picard’s old friend Guinan senses something is wrong. She tells the captain that she doesn’t know exactly how things are different, but knows they are and that the Enterprise in the other timeline is a ship of peace, not war. She concludes that the Enterprise C must go back through the rift. Picard is reluctant to force them to do this because they would be heading toward certain death. Picard has a meeting with his senior staff and they are not willing to do this either, certainly not for the reason based on someone’s intuition only.
Picard tells Captain Garrett of Enterprise C that their presence brought with them 22 years of war that could otherwise be prevented if they go back. Tasha Yar learns from Guinan that they never even met in the previous timeline and that she shouldn’t even be here because she had been killed and it was a senseless death. Captain Picard allows Yar to go and help the C ship go back through the time rift after Garrett is killed in an attack by a Klingon vessel.
I liked this episode because it was very much like a space adventure with a lot of tension, action and human drama without getting too melodramatic. It was well-written and acted.