Original: Eragon and Saphira manage to escape by hiding in the forest, but Garrow is fatally wounded and the house and farm are burned down by the Ra 'zac. Once Garrow dies, Eragon is left with no reason to stay in Carvahall, so he goes after the Ra' zac, seeking vengeance for the destruction of his home and his uncle's death.
Simplified: Eragon's uncle, Garrow is killed by the Ra 'zac (insect-like creatures that work for Galbatorix), who want to find and capture Eragon and Saphira.