God orders the people to keep (or start, really) being just and to observe the Sabbath, so that they'll be saved.
He promises to take care of the foreigners and the eunuchs who've been joined to his people, saying that he'll give them "an everlasting name" if they maintain his covenant.
He also tells the eunuchs to quit complaining that they are only dry trees. Which is actually a pretty poetic complaint, all things considered.
God will bring the foreigners who honor him and keep the Sabbath to his holy mountain, where he'll accept their sacrifices and offerings. The Temple there will become a house of prayer for everybody (you, too, dry trees...er, eunuchs.)
More people are going to get brought into this covenant than the people who've already been gathered together. Despite all the lovey-dovey-ness, God switches back to some condemnation.
He sends out a formal invitation to all the wild beasts of the forest, inviting them to take advantage of Israel's lax defenses, since the Israelite sentinels are like silent dogs, unable to bark, just snoozing.
He says that the shepherds (of the people) are also ineffectual, only interested in drinking themselves silly.
God basically thinks a little wild-animal attack would snap Israel out of its funk. Maybe.