Max listens to a small history about the Indian Dream catcher, while Ben and Gwen browse around to look for anything interesting. Ben seems to be bored of his day, but a young girl’s native dance catches his attention. Gwen is puzzled about Ben’s secret “interest” in the culture’s native ways. Wes tells Max that she is his granddaughter, Kai. Grandpa Max seems to remember her back then when she was only a little baby. Ben fixes up his hair, hoping to catch Kai’s attention. Suddenly, the clouds darken the skies, and Gwen wonders if Kai had summoned the skies to rain. They head to shelter from the storm, but it seems that Ben is too occupied about Kai. A lighting strike hits the ground next to Ben, and a beastly figure appears before him.

The giant figure runs off, while the gang finds that they are in danger. Wes yells out a flash flood, and they head out for higher ground. Unfortunately, Kai is caught by the strong push of the water, and she is carried along the stream. Ben attempts to change into Ripjaws, but the activation process seemed to have failed. Instead, Ben decides to go on his own, and he jumps on top of a barrel. He tells Kai to grab his hand. Suddenly, they notice a wall that may crush them if they continue down the stream, but luckily, they jump up to hang on. Kai thanks him, and wonders why he still holds onto her hand. He lets go immediately and blushes. Up on the roof, the strange creature rips off the satellite receiver.

Wes believes the creature was the Yenaldooshi, a Navajo werewolf. Wes readies up to tranquilize the beast. Unfortunately, Kai and Gwen cannot come along with them, as Wes states that only Braves can head out. The times have changed, but the traditions have not. Ben seems to feel sorry for Kai that she can’t come along with them. Gwen suspects that Ben has a crush on her. Ben at first denies it, but he could not hide it from her for so long.

Outside, Wes tries to find ways to track it down, and they follow the path to where it might be. They climb up the mountainous terrain, and find the beast scavenging through metal trash. Wes readies his tranquilizer and shoots, only to miss it. The mysterious beast comes and attacks them, and they fall off from the cliff. Ben activates the Omnitrix, intending to change into Stinkfly, but it malfunctions and transforms him into Wildvine instead. Wes is amazed by the sight. Wildvine holds on a boulder back at the top of the cliff, and he extends his arms the opposite way to bring Wes and Grandpa Max down to safety. Grandpa Max has some explaining to do to Wes after revealing that Ben can change to aliens.
Wildvine heads back at the top, and he tries to grab a hold of the giant wolf beast. It bites him, and it drags him into the ground. As they head back up to the surface, Wildvine changes back into Ben, and the giant beast comes up to him and scratches his wrist, but luckily it went after his Omnitrix. The Omnitrix starts to react and turns yellow, but Ben doesn’t understand what is happening. Wes and Grandpa Max heads back up to make sure that Ben’s okay, and they head back home.

At the Rust Bucket, Kai questions his grandfather why the people are leaving. He explains that they fear of the werewolf, and with the full moon, its power may be greater than normal. She heads up to Ben and he brags to her how he uses the powers of the aliens in the Omnitrix for good. As he talks to her, he scratches himself, and his irritation doesn’t seem to stop. Gwen mocks him and calls him a monkey. Ben takes his shoe off, and his appearance changes. He turns into a bluish color, claws appear, and he grows more hair. It seems that Ben has been bitten by the Yenaldooshi.

Wes explains that the only way to reverse the spell is to stop the Yenaldooshi that bit him. Ben thinks that a silver bullet would do the work. Wes says that it only happens in the movies. He continues on, and he says the only way to stop it is to acquire the spiritual silver pendant, and get the fluids of a holy cactus, and place it in the Yenaldooshi’s heart. If they don’t do it in time, Ben is doomed to stay as the demon forever.
Ben, Gwen, and Kai are inside the RV, and Ben prepares a bowl full of eggs and pours a liter of milk into it. He immediately digs into the bowl, and he makes a mess. Kai and Gwen are puzzled by his strange animal antics. Gwen finds some info where to find the Arbol el Matrimono cactus, and Ben heads to the fridge to find more food to eat. Suddenly, Ben’s appearance changes even more, and his body has become more muscular, and his head has become more wolf-like. Ben says that he still feels normal, but he heads out to find something else to eat.

Wes hears the beast has struck again, pillaging a radio center. Wes concludes the beast is doing this be cause it believes technology is ruining it's sacred land. Wes, Ben, and Grandpa Max head out to find the beast, and Ben howls in the night hoping to find it. It responds, and they head to the direction where the howl was heard. Wes finds a track on the floor, and he says that he senses the presence of the demon nearby. Behind them, its eyes glow an eerie greenish color, and it revealed itself to be Ben, literally referring himself as Benwolf. Meanwhile, Kai and Gwen are out looking for the cactus. Gwen says that she is ready to give up looking, but in an ironic twist, she sits on it. With both Wes and Kai without reception, Wes uses a flare to call them.

Wes, Max, and Benwolf find that the wolf is right on top of them, the wolf jumps down and attacks Benwolf. Ben struggles fighting the giant beast, and Grandpa Max hits it to distract it. Benwolf attacks back to keep it away from them, and Kai and Gwen get up in time with the cactus. Wes crushes the fluid out of the plant, and he heads to the beast to place it on its chest. It struggles out of their grip just in time before Wes even touches it. Gwen decides to give it a try while Benwolf grabs a hold of it. She places the silver pendant, but no luck. It runs off. Wes is puzzled why the pendant didn't destroy the wolf, when suddenly, Ben started to change again, and to Ben's surprise, the Omnitrix icon appears on his chest. And then everything becomes clear, they are not dealing with a Navajo werewolf, they are dealing with an alien werewolf. Ben remembers that when the werewolf struck the Omnitrix, it glowed yellow, it seems the Omnitrix has the power to absorb the D.N.A of any alien who touches it. Grandpa Max is astounded that by the fact of alien werewolf, stating just when he thought the summer couldn't get weirder. Ben is sulking that he encountered many aliens, and he could have turned into them if they touched the Omnitrix, including Vilgax. Suddenly, the ground starts to shake for some reason. The group discovers a cave and enters. There is a faint smell of sulfur in the air, which tells them that they are inside a volcano. Wes says the volcano is dormant. Just then, the walls crack and lava comes out. The werewolf has somehow reawakened the volcano!
As the group run for safety away from the lava, they find themselves in a more twisted situation: a broken path and a pool of lava below. Luckily, Benwolf was powerful enough to jump and get the girls to the other side of the ledge. But in order to get Max and Wes to safety, he opens up his jaw cavity and uses his sonic howl to propel them to the other side. Wes and Max make it, but Benwolf falls to the edge just the Omnitrix discharges. Grandpa Max comes to the rescue. Ben is back to himself again, only now, he has Benwolf as a choice in the Omnitrix.

The group wonders what the werewolf's true intentions are. As they try to find a way out of the cave, the alien wolf finds them and attacks them. As if that wasn't enough, the lava had broken through and if not stopped, it would destroy the village. Ben decides to turn into Cannonbolt. As the fight rages, they lava flow continues its path down the mountain. Cannonbolt says he'll seal it up and for the others to run. A cave-in occurs, cutting Ben and the werewolf off from the group. The group runs out the cave exit just as the cave roof collapses. They fear Ben is gone, when suddenly he pops up, unharmed. It appears the lava has been stopped and the wolf has been defeated.

At the village, Wes is glad that some of the people are coming back. Though they never found the equipment stolen by the wolf, they feel the threat is over. Ben is happy to have a new alien in the group and plans to add more. As Wes helps Max prepare to leave, Ben talks to Kai again, and shows off, but it seems that she knew what he was trying to attempt. Unfortunately, she says that he is not her type. This crushes Ben. Kai liked Ben as Benwolf, because she wanted to treat him like a dog. This angers Gwen, who tells Kai off, and Kai heads off. Gwen tells Ben that there are other girls he can get, and there are two words that will catch their attention. Immediately, Ben reacts and complains to Gwen for the phrases.
Deep inside the cave, a strange machine made from the stolen transmission equipment rests. Suddenly it activates. Whatever the werewolf was up to was part of a bigger plot.