The Ultrasaurus arrives in an area where there are a lot of islands and finds the one where the gravity cannon is ready to be installed onto it. Krueger is taken to Guygalos to recover and rest, and Rudolf arrives. Then everyone looks at the gravity cannon, and are surprised at how huge it is, but they have to equip it on the Ultrasaurus quickly or the enemy will find them. Meanwhile, Hiltz has arrived in the islands and sends lots of Sinkers to find the Ultrasaurus. At a meeting, Dr. D explains how the gravity cannon works. There are two parts to it, the actual gun and the power generators. The shell is made of a very dense material that has its own gravitational field, and will make a "black hole" when it hits its target. The only problem is that there are only three shells, and one must be used for a test shot. Karl is appointed to aim and fire the gravity cannon.
Van, Thomas, and Irvine check on their Zoids. The gravity cannon is linked to the Ultrasaurus. Fiona is worried about the Death Stinger and Dr. D figures that she can sense it because she's an ancient Zoidian. Hermann watches while Van, Irvine, and Thomas take a short nap, but then the cannon is ready for testing so they all wake up. Meanwhile, Raven gets some water and takes it to his house, where Riece, who is sick, is resting. She tries to punch Raven when she wakes up, but Raven stops her. Later, Raven and Riece drink coffee and Raven tells her that her Geno Saurer was beyond help, but Specular is still alive. Riece wants to get back at Hiltz.
Everyone gets ready for the test shot of the gravity cannon. The target points are set and the shell is fired by Karl. It lands on the sea and explodes, making a "black hole" and sucking all the water to the center. The test shot was a success! Karl sees that the shot drifted a little so he'll have to correct that. Then Sinkers approach and Van in a Pteras, Irvine and Thomas in Hammerheads, and some other pilots fight them. They manage to shoot down all of them but two missiles are headed towards the Ultrasaurus. Van manages to shoot the missiles before they hit the Ultrasaurus. Later, Rudolf leaves in a Redler and Riece tells Raven that she's going to go to Zoid Eve and that Shadow will be there.
Synopsis taken from www.zoidsevolution.com