- "I might have not been here long, but I learned one thing: Everything you told me about humans is wrong. They're good people and they are worth defending." - Kara Kent, to Zor-El, Blue
When Reeves Dam was destroyed during Clark's battle with Bizarro, Kara's ship was released. Kara awoke from her 18-year slumber and she saved Lex Luthor from drowning. Later, she changed into Earth clothing and flew away from the Smallville Water Tower into the sky.
While investigating the area near the destroyed dam, Clark and Lois came across Kara's ship and when Lois approached it, she was knocked out by Kara. After a brief battle with Clark, Kara flew into space and started searching for young boys, hoping to find the baby Kal-El. After Clark found her himself and revealed that he was Kal-El, Kara was shocked and surprised to discover that her infant cousin was now physically older than she was. When Kara learned that their home planet exploded, Kara was devastated but Clark consoled her saying that they were family and allowed her to stay with him on the Kent Farm.
After her ship goes missing, Kara and Clark went in search of it before it can explode and find the ship just in time. However, when Kara stops the explosion, the ship disappeared and the blue crystal that her father warned her to protect with her life was also feared lost.
Clark began to help Kara to adapt to her new life on earth but was worried since Kara still didn't know how to control her powers and especially because she focused more on finding her lost crystal. On the Smallville Harvest Festival, Kara tried to fit in and entered the Miss Sweet Corn beauty pageant, much to Clark's regret and was involved in a problem when other contestants tricked her to help them steal a Smallville treasure (which happened to contain a Kryptonian object that Kara saw) and was arrested for breaking into the treasure just when she won. After saving Clark from the girls, proving she has learned to control her abilities, Clark and Chloe proved her innocence and Kara was free again. Then she was hired at the Talon and began to call the attention of Lex, who accused her of being the one responsible for saving his life.
One morning Kara was abruptly confronted by Martian Manhunter, who accused her from being a traitor and revealed that her family was forced into exile by Jor-El. Kara spied on a conversation between Clark and the Martian where he instructed Clark to find her crystal before she did and then she went in search of her crystal for her own and asked Jimmy Olsen to help her. Later, she was disappointed in Clark for not trusting her and flew out into the night, leaving the farm.
On her search for her missing crystal, Kara flew to Washington, D.C., only to discover that it was missing. After learning that Lex may have some connection to the whereabouts of the crystal, she went to the Luthor Mansion but was subdued by Agent Carter and later taken to a lab where she was experimented on and forced to relive a memory that her father Zor-El had erased, learning that Zor-El did try to assassinate Jor-El and wanted Lara for his own.
Kara apologizes for everything she had done and then returned to live with Clark and Lana to the farm, leaving behind her search of the crystal not knowing that Clark had already found it.
Finally, after Clark started to hear the voice of his biological mother calling for help from Kara's crystal and decided to release her, Kara was happy to see Lara again for the first time in years, but was upset to learn that Clark had hidden her crystal. Thanks to Clark's action, a clone of Zor-El was also released and Kara was able to saw her father again but was upset by what he had done to her and her loved ones. Zor-El claimed he had changed and convinced her to trust him again. After learning that her father wanted to conquer Earth by causing an eclipse that would wipe out all of humanity, Kara tries to stop him but failed and was almost killed by her own father.
After Clark saved Kara and destroyed the crystal, Kara disappeared and woke up in Detroit, with total amnesia and no powers. Kara wandered into a local diner and was given a job (as well as a place to sleep) by the kindly owner.
For weeks and adopting the name "Linda," Kara worked as a waitress and became close to a busboy named Finley. However, when Lex tracked her down and offered her treatment to restore her memory, Finley became obsessive and abducted her and Lois, who was following Lex. Lois told Kara about her name and some of her past and when Clark rescued them, Kara returned to Smallville, but was disconcerted by Clark, believing that he was hiding something from her.
After a meeting with Lex at the Talon, Kara's trust in him grew closer and Lex promised her a treatment that would restore her memories completely.
After Kara demanded the truth from Lana about what Clark has been hiding from her and Lana refused to admit anything, Kara declared that she would uncover the truth, as well as realized that she could not trust Clark or Lana anymore. She turned to Lex and he allowed her to stay at the mansion with him. After a while, Kara became very close to Lex and really happy staying with him.
Kara looked through her "alleged biography" and could not find any clue to her past and after Chloe and Lana kidnapped her from the mansion and took her to the Fortress of Solitude, Chloe pleaded with Jor-El to restore Kara's memory and powers so she can save Clark, who was in danger. Jor-El returned Kara to normal and she was able to save Clark.
Kara never met Lex again after that.
After Kara was approached by Brainiac at the farm and was threatened by him for unknown reasons, she suggests that it would be helpful if Clark could fly to defeat the machine and started teaching him how to fly. When Brainiac attacked Lana to deliver a message to the cousins, Kara went to the Daily Planet and accepted Brainiac's proposal of leaving with him to save Lana. Kara then flies with Brainiac out into the darkness of space and disappeared completely.
While Clark was trying to find a way to locate Brainiac and Kara, he looked through Dr. Virgil Swann's journal, only to find a new message had appeared from Kara on how to save Lana through the Fortress of Solitude. Clark went to the Fortress, only to hear transmissions of Kara from Krypton which suggested that she went back in time with Brainiac through the vortex, as well as that Brainiac was planning to kill baby Kal-El so he wouldn't grow up on Earth.
Back in 1989, Kara was on Krypton fighting Brainiac to save infant Kal-El so he could safely travel to Earth like he was meant to do. Clark was able to come and assist her in defeating Brainiac despite having no powers on their homeworld and they went back to their own time, as well as returned to the Kent Farm. Brainiac however, had anticipated such an outcome and was able to subdue Kara before she could strike the final blow on Krypton. He imprisoned her in the Phantom Zone, as well as then posed as her.
She was last seen floating in the Phantom Zone. Posing as Kara, Brainiac had killed Edwad Teague and revealed Clark Kent's identity as the Traveler to Lex Luthor. Clark managed to find out about Brainiac and demanded to know about Kara, but Brainiac replied "she's somewhere much worse. (Phantom Zone)"