Rock Jaw: Master of the Eastern Border is the fifth book in the Bone series. It collects issues 28-32 of Jeff Smith's self-published Bone comic book series. The book was published by Cartoon Books in its original black-and-white form in 1998. Paperback and hardback coloured editions were published in February 2007 by Scholastic.
This book focuses on the journey of Fone Bone and Smiley Bone. They travel to the mountains to return a baby Rat Creature back to his own kind. On the way, they are interrupted by Roque Ja (whose name the Bones mispronounce as “Rock Jaw”), a giant and enigmatic mountain lion.
Fone Bone and Smiley trek into the Eastern Mountains to set free the baby Rat Creature, who Smiley names Bartleby, and accidentally encounter the two Stupid Rat Creatures. During an effort to ditch the two, they encounter the giant mountain lion Roque Ja. Roque Ja finds the Bones familiar, knowing that the Hooded One is searching for one of them. He explains the Hooded One fears “the one who bears the star” (meaning Phoney Bone) will rise as a new leader and unite the valley against him. However, Roque Ja remains taciturn about whose side he is on.
Roque Ja escorts Smiley and Fone higher into the mountains, against their wills. The possum kids, who have been tracking them since they disappeared from the Barrelhaven compound days earlier, discover them in the company of Roque Ja and grow concerned for their safety. Knowing Roque Ja hates interlopers in his mountains, the possum kids and their raccoon friend Roderick lure the two stupid Rat Creatures to Roque Ja, causing them to fall off a cliff and giving the Bones a chance to escape, however Roderick refuses to leave until he calls out for all of his other orphaned friends. Meanwhile Roque Ja climbs back up the mountain and he is infuriated.
Rat Creature Temple
The Bones flee the enraged Roque Ja and escape into a tunnel in the mountainside, after a debate with Bartleby, they make it to the other side where they discover a magnificent abandoned temple to the Dragons, and wonder about Roque Ja's tale that the mountains themselves were created long ago when the Dragons fought and pushed up the land. As the Bones try to make their way back towards the valley, they encounter the two stupid Rat Creatures, but before they can give chase, Kingdok appears. He is angry at the two stupid Rat Creatures for deserting him, and attacks them and the Bones, forcing them onto a very narrow ledge.
Trapped on a narrow ledge with the ferocious Kingdok ahead of them, the Bones and the Rat Creatures are forced to edge their way to safety along a precarious cliff face after deciding to die rather than sell out their friends. However, on the way they are attacked by a swarm of locusts. Fone Bone stumbles and falls onto a lower ledge. The locusts try to carry him away, but the medallion given to him by Gran'ma Ben falls from his backpack and scares the locusts away. As the locusts flee, Kingdok vanishes into thin air, having been an illusion generated by the locusts' magic. Thanks to the orphans, the Bones realize the locusts could manipulate Thorn or even the whole valley with illusions, as they press on down the mountainside with a suspicious Roque Ja watching.
Call of the Wild
The Rat Creatures, the Bones and their friends make their way down from the mountains, unaware they are being followed and eavesdropped upon by Roque Ja. As they descend, the Rat Creatures reveal that the current unrest has only come about since The Hooded One arrived, bringing with him the locusts and the strange dreams. At that moment, Roque Ja reveals himself to the party and orders them back up the mountain. Before they can go too far, the real Kingdok arrives and starts to fight with Roque Ja. The Bones use the opportunity to escape (minus the two stupid rat creatures because they tried to hand Fone and Smiley at the last moment and they got bitten by the orphans), fleeing from the scuffle and running down the mountain while Roque Ja gets revenge on Kingdok and kills him. Roderick, the possum kids, and the orphans split up and leave. Bartleby rejoins the pack and the Rat Creatures carry the fallen Kingdok away.