Only One Can Remain is the second episode of the fourth season of LEGO Ninjago: Masters of Spinjitzu.
Plot: Contestants of the Tournament of Elements finally reach Chen's Island, rushing to be the first to see and go into Chen's place. The boat sets dock, allowing the people to escape the ship. The Ninja group together, while Kai loses conscious staring at Skylor. Kai immediately blocks the Ninja's path, telling them that “Ladies first.”
While walking to their destination, Garmadon informs the Ninja that Chen was his former sensei. He then shows them a tattoo he has, which represents a snake. The Heroes of Ninjago reach the underground fortress located in the island. Lloyd questions why his father never told him he had a sensei; Garmadon answers some things are meant to be a secret. Jay jokes around, saying Chen never taught Garmadon to have a sense of humor. Clouse arrives, commanding the contestants to welcome Master Chen. The master stands up, recognizing each person's element. He explains that only one can remain; by winning the player must collect Jadeblades in each round. Garmadon stands up, and asks what happens if they lose. Chen laughs, while saying no one would want to lose. Master Chen brings his servants to welcome each contestant to their room. Jay, however, has mistaken the servants for clowns. Just as the Garmadon plans to follow his son, Clouse interrupts him, banning him from the place. Garmadon makes a compromise with him: he will remain outside, protecting his son since Clouse often uses Dark magic.
The Master of Fire enters his room first. His earliest discovery was his Kai poster. He wonders into his patio curiously, and glances at Skylor, his next door neighbor. Kai attempts to use his Elemental power to win Skylor over, but he quickly realizes his hand was on fire. The Red Ninja screams in pain, then cools the Fire down. The Master of Fire asks what element his love interest has, but she refuses to answer.
Jay's servant welcomes Jay to his current home. She also informs the Master of Lightning the ability to control anything in his room with his electrical power. The Blue Ninja attempts to try, popping out a TV.
Cole complains his bed is made out of solid rocks, accidentally triggering a button at the same time. Wondering what the button does, a shelf opens up, revealing a bunch of food. Following his instincts, Cole automatically runs to the food Chen provided him.
Lloyd checks his new Tournament gi, but is quickly interrupted when Master Chen announces the competition starts now.
Lloyd runs to a Jadeblade close to his room, but other attendants of the tournament also compete for it. While getting close, Lloyd is rushed by Ash, narrowly outsmarting and defeating him. Clouse sees Lloyd, and then uses Dark magic to prevent Lloyd from winning. However, Garmadon sees this and attacks him, therefore interrupting his spell. Jay, on the other hand, is taking a shower, when Bolobo enters his room, trying to find a Jadeblade. The Blue Ninja soon puts on a towel and knocks him to the floor, only to find a jadeblade in a light. Bolobo takes it, prompting Jay to turn on Starfarer which amuses the Master of Nature. Jay then whacks him with his towel, while commenting his room. Cole, on a full stomach, is searching for a Jadeblade and comes close to obtaining it, only to lose it to Griffin Turner who grabs it from him. Later, while more contestants goes after the same Jadeblade as the Earth Ninja, they eventually bury him; but he soon overthrows them. Invizable quickly get on his feet (as one of the people who tackled Cole for the same Jadeblade) and snatches it. Cole makes a mini earthquake which covers Invizable in dust, giving Cole the chance to knock him out. He grabs the blade and raises it in triumph, but Gravis takes it. Ironically, another blade was on the floor, allowing Cole to take it silently. Kai and Skylor see a Jadeblade on top of their roof. Skylor preforms back flips to get to the location of the blade. Kai jumps up too, and accidentally knocks her down. He managed to grab her leg, stopping her from falling. He flings her up; however, she reaches the blade, now making only one Jadeblade left and Karlof heads to the last one. Kai realizes and follows Karlof. Kai's archenemy won the battle, but before Karlof could hand it in, Kai unscrewed his Metal fist, getting a chance to win. Kai flies to Chen's location putting the blade in its spot to win.
Since Karlof has lost the contest, he is sent to Chen's secret location in the dungeon. Kai suggest they have a meeting later in his room. The Ninja had entered Kai's room with the exception of Jay since Skylor has arrived, therefore making the Red Ninja push Jay. After Skylor had re-entered her room, Kai helps Jay get up, apologizing for the mishap.
The Ninja discuss the tournament while Cole lays down on Kai's bed, accidentally triggering a button again which reveals a secret entrance. Cole informs his friends, and they silently travel to the secret room. In the secret cave, Kai, Jay, Lloyd, and Cole hear Skylor shout in her room. They observe her room with little peeking holes, and surprisingly find her using the Fire element which makes Cole tease the Red Ninja singing that Kai's heart is on fire. Soon, the Ninja face Chen's minions, but silently hide behind a rock while defeating the four minions. After they defeat the minions, they take their outfits to blend in and look like an Anacondrai Cultist, and go to Master Chen.
Master Chen blurts out that they have captured Karlof, and steals his power with his Staff. However, he uses Ice to capture the Metal element, which the Ninja find interesting since Zane has Ice powers. Their discussion quickly goes to a stop, when their tattoos (which are made out of chocolate) melts which gives away their disguise. Lloyd commands the Ninja to run out of the place; Cole trips on a booby trap which sets out traps and a huge snake. Running away from Clouse's snake, they finally make it back into Kai's room. They now promise to stay within the rules until they find Zane.
Clouse strokes his Snake, explaining he knows the Ninja had spied on them.