Professor Avalon sends Bloom on a magical journey to learn more about her powers and reconnect with them. However, Bloom encounters a mysterious Shadow Virus that gives her a severe attitude adjustment. The Winx and Pixies have to stop Bloom before she steals the magical Alfea Codex for Lord Darkar.
Outside, Bloom is training herself by blasting magic at boulders as Avalon keeps her company. When he questions her intense training, she explains that she is feeling anxious as there has been no activity from Darkar in awhile. Avalon also takes note that her powers have not been at their strongest potential in awhile. Bloom affirms this and mentions that ever since Darkar appeared her magical strength has been dwindling. Unsure of what to do, Avalon suggests she rests but that does not give her reassurance because she needs to be ready should the Trix try to steal the Codex. Avalon then tries to comfort her, saying that the Alfea's Codex is in a safe and secretive place that no one knows.
Overcome with emotions, fear and having to bear the burden of keeping Alfea's Codex's location a secret, Bloom tearfully tells Avalon that she accidentally found out it. Avalon comforts her and reminds her to keep that a secret, even to him.
At Alfea, Timmy enters Alfea in hopes of finding Tecna to speak to her. When he does find her, she gives him the cold shoulder and walks off, leaving him unsure of what to do. Tecna complains to Flora (who was right beside her when Timmy found them) that she refuses to speak to anyone who is "illogical" especially since he is a Specialist. Even though Flora tries to reason with Tecna that Timmy could just be very shy, Tecna does not budge and leaves in a huff.
On their way back to Alfea, Avalon explains why Bloom's power is weakening. Because Bloom's power is the polar opposite of Darkar's, she is being weakened. A concerned Bloom wonders if there is anything she do about that and Avalon suggests reconnecting with her powers through her past. Lockette expresses her own concern for Bloom undergoing this journey but both Avalon and Bloom reassure that it will be okay.
In his office, Avalon gives Bloom a warning about the magical journey she is about to enter. But before he begins, he opens the door and reveals that Flora, Musa, Stella, Amore and Chatta were eavesdropping on them. Avalon politely asks them to leave so that he can concentrate. They awkwardly leave with cheeky smiles. With Bloom comfortable, Avalon begins the spell and Bloom starts the journey.
She sees her adoptive parents, Mike and Vanessa but before she could greet them, the journey pulls her elsewhere - to her lineage. She sees her birth parents, Oritel and Marion, and the Dragon. As she tries to get closer, a sinister-looking smoke greets her and begin to entrap her. It sends Bloom into a panic until Avalon snaps her out of it. It seems that this journey has ended and although she wants to try out her powers to test their strength, Avalon advises her not to do so and she listens.
Back in their dorm, Flora, Musa, Stella, Amore and Chatta bombard her with loads of questions regarding her journey. But all Bloom could answer was that she does not remember much, except that she saw her birth parents and the Dragon, which was the most important to her. Musa then mentions writing a new dance track and wanted to show her friends. Her friends follow her but Bloom stays, contemplating on her experience. Bloom explains to Lockette that she feels sad not saying hello to her adoptive parents after they had taken care of her for so long. Lockette comforts her, explaining that they will understand why she could not greet them.
Bloom, feeling comforted, decides to test out her powers despite being advised not to; growing impatient. After transforming, she does feel better but then, a dark, sinister smoke appears and wraps around her. Bloom is now affected by it and her attitude completely changes. When Timmy enters their dorm wondering where Tecna is. Bloom sarcastically reassures him that Tecna is not avoiding him, only to misuse her powers on Timmy and make him uncomfortable (and also taken by surprise). She takes enjoyment on the little torment she gives him, smacking him against the walls, then dropping him in a vase.
Seeing this attitude adjustment and Timmy's current state of strangeness... Musa seeks out Avalon's help. Afterwards, Bloom is back to normal but is not sure what had happened. All she says is that she felt possessed. She then apologizes to Timmy for her actions and he says it is no big deal before returning to Red Fountain.
Stella thinks that Bloom needs to relax, so she has her friends give Bloom and Lockette a relaxing pre-makeover session. After having some fun and about to start the real make over, Bloom is once again possessed by the sinister smoke. She starts heading somewhere. Lockette follows Bloom while the others go get Avalon.
Bloom now arrives at the Secret Archives and Concorda greets her but to her surprise, Bloom is not the friendly person she remembers. Instead, Bloom starts to make a mess out of her library and then destroying the books in order to seek out the Codex. Concorda and her own Pixie Pets try their best to stop Bloom but fail. Bloom now has the Codex in hand and when the Winx arrive, they too try their best to have return the Codex but nothing. So Lockette, tries one last thing a sweet kiss on Bloom's cheek. It works for a second but Bloom returns back to being evil. She then breaks Secret Archives' roof for Darkar's pet, Kerborg, whom he sent to retrieve the Codex.
It is then the evil aura transforms Bloom into Dark Bloom who then angrily question Lockette betrayal, in which the latter responds in fear. The Winx once again, attempt to stop Dark Bloom but unfortunately to no avail as Dark Bloom gives Kerborg Alfea's Codex. All too late as well, because Avalon then arrives after the Codex is stolen to remove the virus and return Bloom to herself.
When she comes to, she receives the news she hoped to never come to reality - the stolen Codex. She asks for everyone's forgiveness and they all understand Avalon now must alert Faragonda of what had occured whereas now they must find a way to retrieve the Codex. But amidst all the terrible new, Bloom does praises Lockette for her bravery and they share a warm hug.
Concorda then gets everyone's attention, after the crisis is over, she now has everyone clean up the mess. Darkar, on the other hand, triumphantly cackles at his success in stealing Alfea's part of the Codex.
- Bloom sees her birth parents for the first time.
- Bloom becomes corrupted by a Shadow Virus.
- Dark Bloom is first shown.
- Dark Bloom gives the third fragment of the Codex to Kerborg, who gives it to Lord Darkar.
- Wave Shield - Used by Dark Bloom against Musa's sound waves but failed.
- Triple Blast - Used by Bloom against the rock.
- Power Ball - Used by Aisha against Dark Bloom.
- Stella's Solar Flare - Used by Stella Dark Bloom.
- Sun Wave Supernova - Used by Stella against Dark Bloom.
- This is one of few episodes where Lockette has a major role.
- Scenes from this episode, episode 27, 28, 29, 31, 33, 34, 35, 36, 37, 46, 49, 50, 51 and 52 were used for the final Winx special "The Shadow Phoenix".
- As the Winx taken in the sight of the archive, Musa is missing one of her purple ribbons.
- After Bloom asks for everyone's forgiveness, Tecna's eyes can be seen through her scanner goggles.
“Umm, listen, I think we should have a talk. Do you have a second?”
“Of course I don't wanna to see Timmy! Why would I wanna see someone who behaves so... illogically!?”
“I dunno, it was exciting to see my parents and the Dragon. But it was weird to pass over my Earth parents who cared for me all those years and not even stop to say hi!”
“Oh, you mean this? Of course not! ...But Master Darkar sure does!”