It starts off with the Trix attacking a school of psychics, where they took control of the students. They get a psychic message from Selina, who offers a plan to take down the Winx. At Alfea, the Specialists and Paladins were training through the obstacle course. They finish their workout
and decide to go see the girls. Riven decides to stay behind, and Kiko engages in a play fight with him, which ended in humiliation. With the Winx, Flora is still perplexed at Eldora's flower, and Bloom suggests taking it to Palladium after his Potionology class. The Pixies decide to break into his lab to see what is going on. During the class, Palladium begins his lecture on Potionology and uses his lesson to restore the three freshmen students who had been turned into frogs by the Trix a few episodes back. He gets annoyed when he sees the Pixies accidentally make a mess on the table next to him and shoos them off. He resumes his lecture on how to make metamorphosis antidotes, which Roxy takes an interest in. He then tells Roxy to work her animal magic to amplify the potion he mixed to use on Crow Griffin, who then reverts back to herself. Griffin was woozy and nearly collapsed, but is caught. She insists on seeing Faragonda quickly, but Palladium has his students take her to the infirmary to recover. Flora then quickly asks Palladium about Eldora's flower and if he could identify it. Unfortunately, even he could not, but he was surprised to hear the name Eldora. He reveals a fairy of that name once lived at Alfea and taught floral magic at the school's greenhouse. Flora was shocked to know there was a greenhouse on the campus without her knowledge, and Palladium said it was because it had been closed and abandoned ever since Eldora left, locked away in the vaults. An excited Flora runs to where it is followed by the others.
Back at Alfea, the Winx were prepared to head for the vaults, then were met up by the Specialists, minus Riven. Musa asked about where he was, and Timmy responded that he stayed behind to train more, but he said hello. Musa looked away disappointed. Bloom was happy to see Sky again, then gets taken by surprise when Selina suddenly showed up. Bloom introduces her to the others as her childhood friend growing up on Gardenia, then asks why she was in Egypt. Selina claims to have also been in search of Eldora as she was her fairy godmother and due to her connection with her and her magic, the Trix tried to kidnap her. Bloom assures her that she will be safe with them. Sky, however, was a bit suspicious, and asked her how she even knew where to find Bloom, who replies it was her "fairy instinct". She offers her help to find Eldora, which the girls accept. The boys see the girls off, and Sky still senses something off about Selina.
They reach the Alfea vaults, which Flora opens. Before entering, Tecna stops Selina, as she points out that only Alfea students and faculty are allowed to enter, and those who are not should get clearance from Faragonda. Selina argues there is no time for that, and Bloom vouches for her. After Stella spells appropriate outfits for the girls, they enter, which was like a huge exotic forest. Flora then pulls out
Eldora's flower, where Bloom asks if Selina recognizes it. She replies she does not but the answer could be found in the greenhouse. They all split up to find a matching flower. While the Winx were looking about, Selina curses a batch of roses. Once Flora goes to smell the batch, she immediately collapses. Bloom is shocked to find out she had been poisoned, Bloom did not know what to do as the only one who could counteract floral poisons is Flora. Selina asks if there is a potions lab in the greenhouse, and Stella asks how she would even know what to do. She replies she learned floral magic from Eldora, so she would know how to counteract it. Bloom takes Selina with her to find the potions lab. Aisha suggests going to get Palladium in the meantime. When no one was looking, Selina secretly curses a set of plants turning them into huge plant monsters that attack Stella, Musa, Tecna, and Aisha, trapping them in the greenhouse. The four transform to fight the plant monsters and protect the incapacitated Flora.
Bloom and Selina find the potions lab, then a plant monster breaks through the window. Bloom transforms to fight it and tells Selina to concoct an antidote. Selina smirks as all was going according to plan. She spikes it with a lethal poison and proclaims to Bloom she made an antidote just in time before tossing it to her. She tells Bloom to hurry and get it to Flora while she takes care of the plant monster. Once Bloom left, Selina simply reverts the monster to its former state. The Trix observed the event from Cloud Tower and were impressed at Selina's subterfuge.
At the Alfea infirmary, Griffin tells Faragonda and Palladium how the Trix had taken over Cloud Tower and how they plan to take over all the schools in the Magic Dimension. Faragonda assures that they will be stopped. Sky then walks in and asks Faragonda about the whereabouts of the Winx, bringing up his concerns about Bloom's friend, Selina. Griffin's eyes widened at the name and quickly tells them all that Selina is in the employ of the Trix. Sky's instinct was proven to be right and quickly goes off in search of Bloom and the others to warn her before it is too late.
Stella, Musa, Tecna, and Aisha continue to fight off the plant monsters until Bloom arrives. They tell her to go help Flora while they deal with them. Bloom comes down and was about to give the potion to Flora, until it was shot out of her hand by Helia, much to her confusion. She looks up to see the Specialists,
Paladins, and Palladium in the greenhouse. Sky tells Bloom that the potion she almost gave Flora was no antidote. Bloom was confused as to how since it was given to her by Selina, and Palladium points out that it was actually a poison. She became horrified realizing she had come close to accidentally killing Flora. Palladium quickly gives Flora the real antidote. As the guys assist the other girls in staving off the plant monsters, Flora, finally recovered, gets up and reverts them back to normal. All cheer at the victory, but Flora noticed Bloom feeling traumatized.
At the gates, Bloom is in a state of self-loathing, blaming herself for what had happened, because she trusted Selina, and nearly got the others killed for it. Daphne and the others try to reassure her that she could not have known since she had been deceived, but Bloom insists she needs to leave for a while. The girls were disheartened to see her leave. Sky meets up with Bloom and also tries to reassure her, but she tells him she probably does not believe in herself anymore. With a heavy heart, Bloom leaves for Earth.
- Griffin, Carol, Evy and Lorie are back to their original forms thanks to Roxy and Palladium.
- The Winx, excluding Bloom, meet Selina for the first time.
- Bloom almost poisons Flora with the poison Selina gave her.
- The Winx find out that Selina is working for the Trix.
- Bloom decides to go back to Gardenia.
- Winx Club
- Howling Storm - Used by Stormy against the students of Zaltora.
- Devouring Chaos - Used by Trix against the magic crystal and the students of Zaltora.
- Natural Gate - Used by Flora to open the Alfea Greenhouse's gate.
- Unfathomable Fire - Used by Bloom to defend herself and Selina.
- This is the third time Bloom leaves the Winx Club. But it is the first time that she leaves the Winx for almost killing one of her loved ones.
- This is the first time Bloom almost killed Flora, excluding her attacking the Winx in Episode 219.
- This is the first time the Winx enter the Alfea's Secret Greenhouse.
- Interestingly, no one recognizes the Legendarium on the string around Selina's skirt.
- This episode aired in the US as part of the online magic marathon.
- Flora is the second Winx Club members to go weak in this season. First was Bloom.
- This is the third time Nickelodeon Canada airs this episode (July 20, 2014).
- This episode was originally titled by "The Greenhouse of Alfea".
- In one scene, Icy's collar is blue instead of black.
- When the Specialists & Paladins were training, Sky's gem is yellow instead of blue.
- In one scene, Lorie's bracelet is missing.
- When Flora was holding the Lenugia, Flora's bracelet has two straps instead of one.
- In one scene, Musa's hair at the back are missing.
- When the guys visit the Winx, Riven was along with them although he stayed behind to keep training at the Alfea Gym.
- In one scene, Helia's gem is blue instead of orange.
- In one scene, Timmy's gem is light yellow instead of yellow.