Continuing where "Blackbot the Pirate" left off, Dr. Robotnik, Scratch and Grounder arrive in their time machine at the location of the second Chaos Emerald, Medieval Mobius. Robotnik finds the lair of Merlynx the magician. Merlynx is experimenting with potions when Robotnik kindly asks him for the Chaos Emerald of Invincibility. Merlynx refuses, but after a simple threat from Robotnik, he gives it to him. Robotnik holds the Emerald and declares he is invincible. Scratch and Grounder shoot him with lasers to test it out and Robotnik gets fried. Merlynx explains that in order for it to work, you have to become King of the Hound Table.
Back in modern day, Sonic and Tails are enjoying a day at the beach when they are once again approached by Professor Caninestein who tells him he needs to go stop Robotnik again. He gives Sonic the time-space coordinates and the Atomic Relativity Boots. Sonic and Tails leave immediately through time and arrive at the castle of King Arfur where they meet Princess Gwendolyn who has a shuddering problem. King Arfur tells them that his Knights are currently getting clobbered by the "Evil Bloated Knight". Sonic and Tails peek out the window and recognize the bloated knight is Robotnik. The Princess informs them of a legend which states a "Holy Hedgehog" would rescue them.
Robotnik defeats all the Knights of the Hound Table and storms the castle. He sees Sonic and freaks out. Sonic and Tails protect the castle from Robotnik, Scratch and Grounder. Eventually Robotnik makes Merlynx cast a spell to turn Sonic's feet into solid rocks. Robotnik gets King Arfur's crown and activates the Chaos Emerald which makes him invincible and very buff. He places Sonic and Tails in the dungeon. Princess Gwendolyn brings them Chili Dogs with files hidden inside and tells them to find Merlynx.
Sonic and Tails very slowly escaped and made their way to Merlynx's lair. Robotnik sends Scratch and Grounder after them, but Sonic uses his stone feet to stomp them. Merlynx turns Sonic's feet back to normal.
Sonic challenges Robotnik to a joust. Robotnik has the upper hand at the joust until Sonic plants a cactus that Robotnik runs into and loses his helmet that has the Chaos Emerald in it. Tails catches the helmet and obtains the Emerald then puts the helmet back on Robotnik, making him think he is invincible again. Sonic beats up Robotnik and cuts off his armor leaving him in his underwear. Tails uses the Emerald to become invincible and he beats up Scratch and Grounder. Robotnik grabs Merlynx's wand and makes some villagers into Knights which Sonic quickly defeats. Sonic then knocks Robotnik into the moat with the alligator.
Later, King Arfur knights Sonic, calling him Sir Sonic the Speedy. King Arfur now has the Chaos Emerald and is invincible. Sonic sends Robotnik, Scratch and Grounder in their time machine to an ancient Roman Colosseum where they are stuck with an angry lion.
Sonic narrates, saying not to go swimming alone at the beach or in a pool. while Sonic talks, Tails is in the water getting attacked by an angry shark. Sonic was a Lifeguard to save Tails and says to always take a buddy while swimming.