Dallas isn't the only thing down in this cartoonish second disaster novel from the man who flooded the earth in the not-bad Cold Sea Rising (1986); Moran's writing abilities also plummet as he posits a giant sinkhole threatening to swallow the Texas capital in 1999. Moran believes in overkill: that sinkhole--which will eat Dallas in three days--isn't villain enough for him, so to raise the ante he tacks on an impending nuclear holocaust as Mexico's maniacal Marxist leader plans to nuke the US over a border dispute. At the heart of the squabble is yet another villain. Texas billionaire Otto Ralt, who has the notion of Idling in the sinkhole with the Rio Grande River--never mind the Mexicans who will die when he blows up the riverbed, sending its waters through secret tunnels leading to subterranean Dallas. Happily, there's one man who can stop all this fury: ace spelunker Jedidiah Heffernan, temporarily cave-phobic but soon charmed back underground by sweet Lucia Hernandez, who wants him to find her kid brother, Paco, lost in caves near Dallas. (""Both my brother and you are trapped in an underground hell. And because you cannot escape yours, Paco will never escape his""). Scooting along in Heff's trusty ""Caverunner""--a subterranean hovercraft--the two rescue Paco, only to learn upon surfacing that the President himself needs Heft to replug the river that Ralt has already unplugged. After a quick tryst, the two return underground and redivert the river. But it's too late; the maniacal Mexican lobs his A-bomb at Dallas anyway, even though the city is already sinkholed. Once again Heft and Lucia ride Caverunner to the rescue, trying to shoot down the nuclear missile; they don't, but they do learn that sinkholes diet on bombs as well as cities. Not dull; but the Perils of Pauline pacing here is matched by Tom Swift characters and preposterous plotting that will satisfy only the most unsophisticated of readers. In all: kid stuff.