A royal party at Palace of Domino is cut short when the Winx learn the Gem of Courage is in Domino's ocean, where they will face a great challenge.
Musa and Tecna are in the dorm doing some research as Bloom, Stella, Flora, and Aisha have gone to Domino to attend a ceremony. The Sirenix Book appears and tells that there is one test left to complete in order to obtain the Gem of Courage, which is hidden in the yellow reef, where they must "snatch courage from its jaws". Tecna is not satisfied with the clue since it is so vague, so she consults her Guardian Spirit. The spirit tells Tecna and Musa that the yellow reef where the gem is at is on a planet that was saved by one person's courage. They find out that it is actually Domino, as it was Sky's courage that saved them from eternal ice (flashback from Secret of the Lost Kingdom). They have to act fast since there is only a mere two days left to their deadline.
At Domino, Bloom takes Sky into the Domino Palace to meet her parents, to get reacquainted with them. She reminds him that it was his bravery that saved Domino from being stuck in an ice age, though he tells her he does not remember that guy who did so. She is still worried about Daphne, and Sky tries to reassure her that she is probably fine.
Outside, Stella was not satisfied with the dresses she, Flora, and Aisha were wearing and finally puts a finishing touch on them before they enter the palace.
At Tritannus' lair, he continues to torture Daphne to make her talk, but she still remains defiant. Icy then casually brings up that a ceremony on Domino was happening today and that it would be a shame if something happened to her parents, making Daphne angry. Tritannus sends the Trix to Domino to capture Oritel and Marion while he goes to Domino's oceans.
Bloom has Sky meet Oritel and Marion, which seemed awkward for Sky since he cannot remember meeting them let alone saving them. Stella, Flora, and Aisha enter to greet the royal couple, but then get a call from Musa and Tecna, telling them the final gem was on Domino. Bloom goes to tell her parents of what she must do, and Oritel tells her to go on, as Sky will cover for her, making Sky nervous.
In Earth's oceans, Phylla, Illiris, and Desiryee escort Serena, the Gatekeeper of Domino, to protect her from Tritannus. As they swim, Desiryee notices something on the ocean floor, which turned out to be the Pendant of Eraklyon that Sky lost back in The Spill. She picks it up, hoping Flora would know what it is. Unfortunately, Tritannus arrives and brushes off the other Selkies before absorbing Serena's powers. He breaks into the gate and Illiris and Desiryee follow while Phylla stays with Serena.
On the Odyssey Explorer, Bloom, Stella, Flora, and Aisha arrive above the Yellow Reef and transform to go under. They encounter Illiris and Desiryee, who tell them that Tritannus has passed through and Serena weakened. They take the Fairies to Serena, being escorted by Phylla, and Serena immediately bonds with Bloom, restoring her powers. Desiryee then gives Flora the pendant she found, which she recognized as the Pendant of Eraklyon then keeps to return to Sky later.
Back at the palace, Oritel and Marion begin the ceremony of Domino's liberation as they present the Sword of Domino, and Sky, who was still nervous about the whole thing. Suddenly, the Trix crash the ceremony and attack. Darcy easily takes out the guards by forcing them to fight each other. Sky, Oritel, and Marion immediately arm themselves to fight. Sky tells them that he still cannot remember how to draw his sword, but Marion tells him that there is a time for talk and a time for action before they all charge.
The Selkies lead Bloom's group to the Yellow Reef, where it gets tainted by Tritannus' pollution, causing the reef to mutate into spiky deathtraps. Bloom and the Selkies manage to escape its confines, but Stella, Flora, and Aisha were trapped within the spikes. Stella found to her horror that attacking the spikes would just only accelerate their growth. Aisha tells Bloom to do something before they wind up pin cushions. Bloom has Serena locate the source of the pollution, which was a crack in the ocean floor seeping out oil. Bloom quickly blasts it, sealing the hole and reverting the reef. They then find the Gem of Courage, a green gem, floating nearby. Just as Bloom was about to retrieve it, it gets swallowed by a monster fish, which begins to attack them. They find to their shock that none of their spells were working on it, and Bloom decides to try one more thing, which was to literally "snatch courage from its jaws". Stella, Flora, and Aisha try to stop her, but Bloom swims directly into the monster's mouth, apparently eaten. Suddenly, the monster fish glows and explodes into sparkles, leaving behind Bloom and her prize, the Gem of Courage. Their Sirenix Boxes get completed with five gems now adorning the points. At Alfea, Musa and Tecna found their Sirenix Boxes also upgraded.
At the palace, Oritel and Marion were holding their own against the Trix, saying they are nothing compared to their ancestors. The Trix employ dirty tactics to capture Oritel and Marion in dark nets before finally turning them into ice statues. Sky gets angry and demands them to let them go, but gets shot down. Icy then calls up Tritannus, who was with Daphne. Sky managed to catch this, realizing Daphne was being held hostage. Tritannus forces her to watch in horror as her parents were iced over. When Icy cruelly pokes Marion's ice sculpture while mockingly wondering if she would shatter if she fell over, Daphne finally broke down and agreed to tell Tritannus everything. Tritannus calls the Trix back.
Before heading back, Icy decides to shatter Oritel and Marion anyway for cruel amusement. Just as she, Darcy, and Stormy launched a combined attack on the defenseless ice sculptures, Sky jumped in and destroys the attack after arming himself with the Sword of Domino. The Trix get angry for the interruption, but then get jumped by Bloom's group. Bloom was horrified at the state her parents were in and she immediately fights back. With help from Sky and the other Winx, they curb-stomp the Trix yet again, who immediately retreat as they have done what they came to do. Sky wonders how they can revert Oritel and Marion back, and Bloom simply says together. Joining hands, power flows through the Sword of Domino, and Sky taps it on the royal couple, reverting them back to normal. Bloom was happy to see her parents alive and well again. Flora then presents Sky the lost Pendant of Eraklyon. Once Sky touched it, memories flooded back into him. Bloom was happy he regained his lost memories, and he finally presents the pendant to her. It seemed all was right, but then Sky remembered what he had witnessed earlier. He tells Bloom that Daphne had been taken hostage by Tritannus and that he had already forced her to tell him everything about the secret of Sirenix.
- Bloom obtains the Gem of Courage, officially ending their Sirenix quest.
- Desiryee finds the lost Pendant of Eraklyon on the ocean floor.
- Sky finally recovers from his amnesia.
- Sky finally presents the red heart-shaped Pendant of Eraklyon to Bloom, which he had tried to do since the season started.
- Bloom bonds with Serena, thus restoring all of her abilities.
- Tritannus succeeds in making Daphne reveal the secret of Sirenix to him.
- Bloom finally knows that Daphne's in the hands of Tritannus.
- Winx Club
- Tornado Force - Used by Stormy against Domino's guards.
- Dark Chaos - Used by Darcy against Domino's guards.
- Fire Blade - Used by Bloom against the source of pollution power.
- Net of Darkness - Used by Darcy against Marion.
- "Freeze into Statues of Ice" - Used by the Trix to freeze Oritel and Marion.
- Dazzling Spiral - Used by Stella against the shark monster.
- Thirteenth Seal - Used by Aisha against the shark monster.
- Green Growth - Used by Flora to stop the shark monster from chasing Bloom.
- Sun Boomerang - Used by Stella against Stormy.
- Morphix Shield - Used by Aisha to protect herself from Darcy.
- The events of the first Winx movie, The Secret of the Lost Kingdom, is mentioned.
- This is the first time Domino is shown in the 2D part of the series.
- This is the first time we see Oritel and Marion in action in the animation that isn't a flashback.
- The Sword of Domino makes its first appearance since the first movie.
- This is the second time Bloom jumped into a monster's open mouth, the first being in "The Monster and the Willow" back in Season 1. Incidentally, both took place underwater.
- According to Tecna, there are over 100 locations called "Yellow Reef" in Magical Dimension. The only known one is in Domino.
- Interestingly, it seems that Domino's Ocean Gate is located on Earth and the oil rig turned eco-friendly one. Evident by the Pendant of Eraklyon being found near it.
- Starting with this episode, all episode title cards will appear in three-dimensional animation instead of two-dimensional animation.
- This is the second time Marion and Oritel were seen frozen. The first time is in The Secret of the Lost Kingdom.
- The alternative title for this episode was "The Domino Ceremony".
- Bloom had flowers on her dress before Stella gave the Winx theirs.
- Lemmy did not appear when Aisha went into Domino's ocean.
- Stormy's "S" decoration was backwards in Tritannus' lair.
- In one scene, the purple gem on Bloom's Sirenix Box is in pink.
“You will not enter the oceans of Domino!”
“Sky, dear, there's a time for talk, and there's a time for action.”
“If I push her over, do you think she'll break?”