Princess Anne tells Louis to head home and order the Royal Mother to stop her search, joining the Teen Musketeers and D-Team to stop Richelieu. D'Artagnan knows of one last old building where the Blue Eye of Gaia might be, the haunted Vasasi Castle, where Richelieu has also been sent, hiding his fear of ghosts. Meanwhile, the Alpha Trio are waiting to congratulate the Musketeers as they pass, the Alpha Jet under a tarp on a large cart, when French soldiers arrive; the Trio claims to be traveling theater actors, but Ursula summons Tank when the lead soldier says she probably plays an old witch. On the Space Pirate Ship, Foolscap reports the Cosmos Stone Detector sent him to a chicken coop, Spectre noticing the signal jumps when he scans again, beginning to suspect sabotage.
Tank swings at the soldiers until Foolscap arrives, attacking them with Ankylosaurus to find the Cosmos Stone and easily defeating them, but leaving empty handed. The soldiers head on, quickly finding the D-Team; Princess Anne keeps them from getting arrested, but the lead soldier insists she go with him to Richelieu to sort things out, Lady Constance joining them. D'Artagnan immediately leads the Musketeers on a rescue mission, the D-Team heading for the Blue Eye instead, but they soon turn back to help, too. At a commandeered inn, Richelieu simply repeats his orders to Princess Anne, leaving her locked in a room; meanwhile, both the Teen Musketeers and Alpha Trio infiltrate the building separately but soon meet up, Ursula summoning Terry when the same soldiers find them again. Using the distraction, the Musketeers find Anne and Constance, but Richelieu captures them immediately, carting them away.
The D-Team, Alpha Trio, and Anne and Constance all head off to Vasasi Castle to intercept Richelieu. The D-Team note the Trio's obvious soft spot for the Musketeers, Ursula confiding that they're all orphans: they were trouble-causing 3-year-olds when Dr. Z (still working on his doctorate) adopted them and Rod and Laura's father, raising them as the henchmen he always wanted. Richelieu is stuck at a bridge over a gorge with a broken wheel when the D-Team catch up, Richelieu convincing the arriving Foolscap to fight them with Ankylosaurus. While fighting his new enhanced Spectral Armor Armatus as well, Anne and Constance head across the bridge at D'Artagnan's suggestion to distract Richelieu, but rubble from the battle sends the Musketeers' prison carriage over the cliff.
The Alpha Jet swoops and grabs the carriage with cables but, now over its weight capacity, crashes on the other side. However, when Richelieu finally spills the Cosmos Stone's location to Foolscap, the Space Pirate withdraws from the easily winning battle and heads for the prize, but is knocked aside by the reverberation of the attack he recalled his dinosaurs away from. The D-Team races across the bridge, but Richelieu orders his soldiers to cut the bridge's ropes and it collapses underneath their feet…
Ursula/Tank vs. Foolscap/Ankylosaurus
Ursula summons Tank to scare away Richelieu's soldiers, flailing her tail at them, but Foolscap shows up and summons Ankylosaurus, who leaps in and knocks Tank aside. The Alpha Trio try to run from the soldiers, but their wagon is too slow. Ankylosaurus dodges a leap from Tank, her next tackle ramming it back, but it uses Mole Attack, launching Tank careening into the Alpha Gang's wagon, defeating her and knocking them into the forest.
D-Team vs. Foolscap/Ankylosaurus/Armatus
Foolscap summons Ankylosaurus, while Rex summons Ace. Richelieu's solders scatter as they circle each other, Ace ducking a tail swing, but is tossed away. Foolscap and Rex upgrade to Spectral Armor Ankylosaurus and DinoTector Ace.
The Alpha Trio tries rescuing the Teen Musketeers, Ursula preparing to summon Terry, but Ace is knocked down the hill at them. Foolscap unleashes the permanently Spectral Armored Stegosaurus, Armatus, who charges Ace; Zoe and Max summon DinoTector Paris and Chomp, Chomp blocking Armatus from Ace while Paris rams with Ankylosaurus. Armatus easily shoves through Chomp before hitting Ace with his tail and shoving him into Chomp, pushing them around the battlefield. Chomp is sent into the mountain wall, rubble separating the Musketeers' prison wagon from its horses and sending it towards the cliff.
The D-Team uses their Ultimate Moves in a last-ditch attempt at victory, but Foolscap recalls his dinosaurs out of the triple attack's path and flies off, having learned the location of the Cosmos Stone from Richelieu. However, he's hit with the shockwave from the attack hitting the ground and knocked into the cliff wall.
- This episode's English title comes from the famous Three Musketeers saying, "All for one and one for all."
- Although this is the second episode in which an Ankylosaurus defeats Tank with Mole Attack, this is the first time that Tank was actually defeated by the Move directly, as the first Ankylosaurus had to hit her a few more times after using the Move.
- With the defeat of Tank, all six main dinosaurs have been defeated at least once in Mesozoic Meltdown while not wearing their DinoTector Armor.
- Yet again, a summoned dinosaur's card zips back to its owner when defeated instead of falling where it had been standing, with Tank's card following the Alpha Trio as they're flung over the forest.
- According to Foolscap, the Spectral Armor that Ankylosaurus wears is the same new and improved Spectral Armor as worn by Gigas, Armatus and Maximus. This claim could be a dubbing error, because Ankylosaurus' Armor is the same as Edmontonia's regular Spectral Armor, is not permanently affixed to Ankylosaurus, and doesn't have its own Spectral Move. Possibly, Ankylosaurus' Spectral Armor was a prototype of the altered Armor that differed from the regular Spectral Armor in that it could withstand attacks better and was more difficult to destroy, but these were never given the chance to be tested.
- This is the only episode where a Space Pirate controls two dinosaurs of the same Element (not involving Move Card Dinosaurs), though two Space Pirates controlled dinosaurs of the same Element once before.
- During the dinosaur fight, when Armatus charges through Chomp to get to Ace, due to an error, Ace is missing, and his CG model spontaneously appears in-frame just before Armatus reaches him.
- Max comments that their battle with Foolscap is still a losing one at "three against one", when it's actually three against two, or, as Paris wasn't even fighting Armatus, two against one.
- When triggering their Ultimate Moves together, the D-Team say "Dino Slash!" as if they're summoning dinosaurs instead, likely by production mistake.
- The shockwave from the D-Team's triple Ultimate attack sounds like Paris' sonic call attack (including her roar) when it hits Foolscap, as if the dub tried recasting it as her interference, despite the next line of dialogue confirming it to be from the prior attack. It may also have either been the same in the original, or was simply used as a stock sound effect.
- This Ankylosaurus is the only Space Pirate dinosaur never defeated in battle, as it makes no further appearances after being recalled.
- Although Armatus makes his debut in this episode, he does not use Spectral Stinger, making him the only main Space Pirate dinosaur that did not use his Spectral Move in his debut. This is a similar case to Ace who didn't use his Ultimate Move on the first dinosaur he fought in his DinoTector form.