Princess Elena is still at Nueva Vista and continues to work on the Scepter of Light's powers. She is practicing the "Bloom" spell, a spell that can get plants to grow and bloom, with Mateo's help but fails. Elena laments that she has had some trouble with her scepter ever since Shuriki blasted it. Suddenly, a messenger appears and reminds her to go to the meeting with her council she had arranged but forgot about.
Elena arrives late at the meeting only to be greeted by Esteban and Naomi are a bit irritated why the meeting was so important since Shuriki is gone and they are on vacation. Elena proposes her idea of signing a unity pact with King Pescoro to officially establish their new friendship. While Esteban is a bit angry because of the interruption, Luisa and Francisco agree with Elena. Naomi, on the other hand, is not very happy about the thought of signing a pact with the sirenas since they did many bad things and helping to defeat Shuriki does not erase this. Elena still wants to give her newfound friends a chance and make up for their misdeeds. The following vote is in favor of the pact with Elena, Luisa, Francisco, and Esteban, after a bit of hesitation voting for it. Naomi still refuses to trust the sirenas and tells Elena she is making a mistake. After that, she storms out of the room and slams the door.
Later that day, Elena swims to Coronado and inadvertently sets off the coral alarm. Daria, her octopus Ocho, and some guards arrive. Upon seeing it is just Elena, Daria tells the guards to leave and shuts off the alarm. She explains that these alarms alert them should somebody who is not a sirena try to get too close on Coronado. Furthermore, she explains that the reason for these alarms are Malandros, nasty shapeshifting river dolphins who cannot stand the sound the coral alarms make. Elena tells her she came to see King Pescoro and Daria, after telling her the magic kelp does not give Elena permission to visit anytime, escorts her to the palace.
At the palace, Elena presents her idea of the pact and a feast after signing it to the King of the sirenas. Daria intercepts and expresses her doubt that one lunch will not make everyone forget the past. King Pescoro is doubtful too but his daughter and wife encourage him to start a new area by signing the pact. Daria thinks it is too soon, but Queen Camilla and Princess Marisa object and Elena manage to persuade King Pescoro into signing the treaty. Daria tells the king he is making a mistake, but he brushes it off and tells her to help Elena with the preperation.
Elena, Marisa, Marzel, and Daria meet at the palace canal. The first problem is which food to serve. While Elena is thinking about a lot of different kinds of food, Daria tells her, sirenas only eat kelp and seaweed. Elena accepts that. Next, they want to find a location. Marzel's suggestion is denied by Naomi, who suddenly appears. She confronts them about the shipwrecks there. Marisa apologizes while Daria is hostile towards Naomi and tells her that humans attacked the sirenas first. Elena decides to choose the location later. Naomi leaves, declaring the best thing to do would be not signing the pact at all. Daria agrees to this and leaves as well. Elena, Marisa, and Marzel continue their planning and agree on a perfect place for the party.
An angry Daria, whose views of humans have been confirmed by Naomi, shows a scar, which humans are responsible for, on her fin to Ocho. Even though this incident happened years ago, she thinks the pact is just a trick to get the sirenas to let their guard down and then attack. Daria declares it is her duty to stop the signing of the pact and swims to get help from the malandros. After getting past Torpe, who is allergic to seaweed, with Ochos help she talks to Saloso. She tells him about the unity pact and that humans are their common enemy. She even says she trusts the malandros more than humans. Saloso does not care about the pact nor does he want to help Daria stop the pact. They make a deal: the malandros help Daria and in return, they get the coastline north of the city and can leave their wrecked accommodation. They plan for Torpe to shapeshift into a sirena, while Saloso is supposed to turn into a human. Then, while Torpe sings as a sirena, Saloso accuses them of still being evil, which will cause the humans to attack them and stop the pact. Before Daria leaves, Saloso tells her to turn off the coral alarms, which she agrees to. After she has left, Saloso tells Torpe to destroy all the deactivated coral alarms.
The next day, everyone is at the coast to celebrate the signing of the unity pact. Elena signs first but before King Pescoro can sign, Torpe, disguised as a sirena, starts to sing. King Pescoro demands this to stop and Marcel pursues the "Sirena". But the humans on the ship have already gotten their weapons and aim at the innocent sirenas, who proceed to return to Coronado. Elena is sad and confused why it did not work out.
The Royal Family of Coronado is on their way back to the palace when they are captured by the malandros and discover the singing sirena was actually a malandro. Daria furiously confronts Saloso, stating that this wasn't part of their deal. Saloso just laughs and tells her he tricked her and taunts the family through song. Saloso then reveals Daria's treachery to the shocked Royal Family. Since the coral alarms are destroyed, the sirenas have no way of getting rid of the malandros and taking back their kingdom. Ocho uses his ink to confuse the river dolphins and Daria and Marisa manage to escape. Daria discovers the destroyed coral alarms and gets chased by some malandros.
Meanwhile, Elena and Naomi talk about the events, Naomi being sure the sirenas are still evil. Suddenly, Marisa emerges from the ocean and gets on board of the ship they are on. She tells them what truly happened and that her kingdom is under siege. At first, Elena is happy because the chance of peace is still there, but quickly changes her tone and wants to help Marisa regain her kingdom. Naomi accuses Marisa of lying. Elena asks why she has been acting that way towards the sirenas. Finally, Naomi reveals that she lost her grandfather because of them, as they sunk the ship he was on. Naomi tells Marisa to leave but Elena reminds her that the sirenas helped them defeat Shuriki and she wants to return the favor. Naomi is still not willing to come with her, but Mateo and Gabe are. They swim to Coronado, with their chest wrapped in magical seaweed. They see Daria being chased and captured by the malandros and confront them. Elena blasts them with her scepter and the malandros swim away. Gabe frees Daria, who tries to get them to leave since it is not their battle. Elena tells her she wants to help because they are allies. Daria confesses she is the reason for the malandros' takeover. Elena forgives her as she just didn't know who to trust and Daria shows them the broken coral alarms. Since it would take to long for them to regrow them, Elena tries using the "Bloom" spell. They get attacked by the malandros, who capture them and take Gabe's sword and Mateo's tamborita. At the last moment, Elena manages to make the coral alarm grow and the resulting noise drives the malandros away. Coronado is saved. Naomi sees she was wrong and is ready to give them a chance. They finally sign the unity pact and celebrate.
- Aimee Carrero as Princess Elena
- Gina Rodriguez as Princess Marisa
- Jorge Diaz as Gabe
- Jillian Rose Reed as Naomi
- Joseph Haro as Mateo
- Edward James Olmos as King Pescoro
- Rita Moreno as Queen Camila
- Prince Royce as Prince Marzel
- Rosario Dawson as Daria
- Steve Buscemi as Saloso
- Ralph Garman as Torpe
- Richard Horvitz as Ocho
- Travis Willingham as Cuco
- Christian Lanz as Esteban
- Emilio Diez as Francisco
- Julia Vera as Luisa
- The malandros are based on the Brazilian myth of the boto encantado, a shapeshifting and enchanted river dolphin. The name "malandro" also gives an idea of how untrustworthy those dolphins are.
- Moral: Don't dwell in the past in a way that makes you unable to see what's going on now or make you trust the untrustworthy.