Somewhere in Texas, people are working to obtain some oil underground. A mysterious earthquake alerts them, and they run as the ground breaks up while the tower falls below. The mysterious quake unearths a large tornado of flames, which then reveal to them a mysterious mask, right before their eyes.
Meanwhile, in the RV, Grandpa Max, Gwen, and Ben are having an afternoon lunch. Grandpa Max asks them how it tastes. Ben and Gwen seem to enjoy its delicacy, but they immediately are turned off after learning that the crunchy bites in the soup are dung beetles. An alarm then sounds off, and one of the cupboards open to release a monitor that showed the mysterious mask. Grandpa Max identifies it as the mask of Ah Puch, and it is the key to the most destructive weapon ever known in the world, the Sword of Ekchuah. Ben is puzzled whether it was another alien. Grandpa Max continues and says that Ekchuah was the Mayan god of war, and his sword is legend to wipe out a city in one swipe. Ben is excited by his theory. Grandpa Max explains that the sword is something not to be used for enjoyment, and it can control the fate of all mankind. Gwen and Ben appear to listen and agree with him.
They arrive at the area where the mask was found, and Grandpa Max tells Ben to transform and sneak in. Ben insists that he would break in instead, but Grandpa Max seems to be very serious about the situation. Ben continues to puzzle his grandpa’s attitude. Gwen explains that he’s just trying to save the world. So Ben transforms into Grey Matter, and he climbs up the gutter. Gwen agrees that Ben can be a bit annoying at times, but she seems to be worried about what Grandpa Max said earlier. Grandpa Max interrupts her and says that they were only kids who don’t understand the problem going on now.
Inside the building, Grey Matter arrives through the drain in the bathroom. Gum is stuck on his head, but little does he know that the place was guarded by two large dogs. He eventually jumps out of the way before they attack him, and he runs out. Outside, Grandpa Max and Gwen wait for Ben to open up the basement door. When he does, it seems that Grandpa Max was very impatient. Gwen picks up Grey Matter and complains of his smell.
They walk through the basement hallways, and Gwen and Ben continue to be aware of their grandfather’s condition. A vault is then at the end of the line, and Grey Matter opens it up. Inside reveals the mask of Ah Puch, and Grandpa Max finally gets his prize that he was not able to obtain forty years ago. Footsteps are then heard behind them, and it was Enoch, the leader of The Organization. It seems that he is after the mask. Before the Tennysons and The Organization go off to a fight, a security guard comes in just in time to distract them. Grey Matter jumps onto Enoch’s face to cover up the eye sockets in his mask, while Grandpa Max and Gwen run out to get the mask to safety. Grandpa Max and Gwen were able to get out, but Grey Matter was almost thrown into the paper shredder. He hangs on for his life, while Enoch and his henchmen go after the mask. Instead of chasing after them, they head the other direction. The security guard then orders the security to lock down the building, to make sure that they don’t head out the building.
Grey Matter was able to jump away from his doomed fate, and Gwen and Grandpa Max continue to run away. They see an exit, but a guard personnel was there. They tried another way. Before reaching the exit, Enoch was right behind them, and his grabs the mask away from Grandpa Max. With a hard decision, Grandpa Max tells Gwen to hold on to his hand, and they were able to get out of the building. Grey Matter manages to get out also, but lands into a dumpster, and transforms back to Ben. Grandpa Max then tells Ben to hurry up, so that they can catch up to Enoch before he gets the sword.
Enoch is inside his car, and he looks at the mask with amazement. The driver then sees the RV in the side mirror, and Grandpa Max is inside. Grandpa Max turns on the aerodynamics for the front bumper, and he accelerates the RV to ram into Enoch’s vehicle. Ben continues to try and re-activate the Omnitrix, but Grandpa Max’s impatience has led him to put the RV in auto-pilot, and heads in back to put on his old Plumber suit. While Enoch’s men try to attack the RV, Grandpa Max jumps out to Enoch’s car and takes back the mask. Grandpa Max sees the mask, but Enoch had a blade to protect it. Grandpa Max slips off from the top of the car after avoiding getting stabbed by the sword, but he manages to get himself back up. The situation is intense, but without Grandpa Max’s protection, the kids are doomed inside the RV, while the henchmen try to go after them. Gwen and Ben however, were able to get one out of the door, and it was shown that they were headed for Mexico.
Their excitement was drawn off after learning that the second man was coming from the RV’s top, but Gwen was able to use the fire extinguisher to let him off the RV, but also fall down the bridge and into the water. Grandpa Max continues to attempt with all his power to try and obtain the mask. Learning that the blade is metal, Grandpa Max was able to use his magnetized pad to hold onto Enoch’s sword, which had gripped on it fairly hard. With Enoch distracted, Grandpa Max was able to take back the mask. A truck was heading nearby in front of them. Grandpa Max tells his grandkids to hold on, but without paying attention to his driving, Grandpa Max turns on the rocket thrusters, which made a great chance for the truck and the RV to collide.
With a quick reflex, Grandpa Max was able to avoid the truck, but too close to scratch the side of it. Realizing that Enoch is behind them now, he releases tire spikes to slow them down. The RV drives away, but Enoch was ready for his counterattack.
Grandpa Max and the kids stop somewhere due to the RV’s breakdown after the recent fight on the road. Grandpa Max complains that he needs the correct wrench, and Gwen finds that their grandpa has been changed completely since they were notified about the mask. Ben tries to look through the mask, and the sockets glow, revealing a hologram that mapped the temple of Ekchuah. With no time to spare, Ben transforms to Stinkfly and flies to the temple instead. Grandpa Max insists for Stinkfly to go faster, but Ben explains that he can’t with too many people with him.
They arrive at the temple, but it seems that Enoch and his men are already at the site. They try to open the pyramid doors with dynamite, but it seems that the stone doors are strong enough to withstand the blast. Grandpa Max and the kids head another way to find a secret entrance to the temple. As Grandpa Max tries to look for a switch, Ben decides to use the mask to reveal its location. A glowing brick was shown, and it opened up the tomb with success. With the path dark, Grandpa Max grabs a torch, but the blinding light almost led Ben into his fate of falling a long way down. Grandpa Max was able to save him, but his obsession in obtaining the sword is his primary priority. They head down the wooden platforms, but before Grandpa Max was able to warn Gwen and Ben of the dangers of the temple, Ben accidentally activates a booby trap. The temple starts to rumble, and begins to release humungous boulders from above, breaking their path from all directions. Grandpa Max was able to use a grappling hook from his uniform to get them out of there. Ben and Gwen were glad to be safe, but Grandpa Max was already far in front. Gwen and Ben don’t seem to enjoy being around with their grandfather anymore.
They find the socket where the mask can be placed, but Enoch was there to stop Grandpa Max before he can do so. He captures the kids, but before Grandpa Max tries to shoot his men holding the kids hostage, he worries about their safety more, and surrenders. To make sure that Grandpa Max and the kids don’t get in the way, he throws them into the Pit of Despair, known to be bottomless. They were doomed and fated to probably never come back.
Meanwhile, as Ben falls down the pit, he was able to re-activate the Omnitrix and transform into Four Arms. Four Arms manages to grab a hold onto the wall, and grab Grandpa Max and Gwen thereafter. They were lucky to survive before falling down the pit, thanks to the Omnitrix. Enoch places the mask into the depression, and a flash from the door indicates its opening. There, a large pyramid shrine rests on top the sword of Ekchuah. Four Arms gets back up with Gwen and Grandpa Max, and Grandpa Max was in a rush to get the sword. Four Arms tries to let his grandfather remember what was important the most, and they continue on.
Enoch’s men were not able to obtain the sword, as there was a guardian protecting the treasure. It was Ah Puch, the Mayan god of death and the underworld. The men were having trouble of trying to control the beast, and it was to the Tennyson’s advantage to use the time to try and go for the sword. Gwen and Grandpa Max try to head up the pyramid, while Four Arms distracts Ah Puch.
It was Grandpa Max and Gwen, about to get the sword. Unfortunately, Enoch was there to stop Grandpa Max from using his hook to get it. Grandpa Max was able to kick him down, but Enoch uses Gwen to distract him from getting to the sword. He realizes that Gwen is more important and comes to the rescue. While Four Arms continues to fight, he notices that Grandpa Max and Gwen are in danger, so he gives Ah Puch a punch, and heads up to save them, but unfortunately, he transforms back to Ben. Ben was able to save Grandpa Max and Gwen from Enoch, and Grandpa Max headed back up to try and stop Enoch. Ah Puch awakens yet again, giving Grandpa Max a choice to either save his grandkids, or go after Enoch and take the sword. He sees that the kids are more important, and heads down to stop Ah Puch. Enoch pulls out the sword, and he gloats for his achievement in obtaining the ultimate weapon, though it crumbles and Grandpa Max laughs at the result. The temple starts to rumble, and Grandpa Max and the kids head out. Grandpa Max insists that Enoch should head out, but he is too greedy to even listen to a request that can save his life.
Outside, they see the temple fall, and Grandpa Max seems to be interested in the Dung Beetle soup again. The kids were happy for their grandpa to be back to normal, but wonder how to get back. Luckily, Grandpa Max still has the knowledge to pilot Enoch’s helicopter nearby, and they fly off