A year and a half, a monster known as Mbwun tore a bloody swathe through the New York Museum of Natural History. Of course, the good guys triumphed by killing it. 
 But the legacy of Mbwun lives on in "Reliquary," which introduces a new grotesque brain-ripping threat to New York City, while revealing some truly shocking twists about the monstrous creature. At times it feels tangled up in social commentary on the homeless and the wealthy, but the central story is a pretty chilling one, even as Douglas Preston and Lincoln Child dive into the filth, abandoned rooms and shadowy subways where the new monsters dwell. 
 A pair of skeletons are found sunken in river sewage, with their heads chewed off and their bones deformed. Since one of them turns out to be a well-known socialite, the police and the news media are immediately being hounded to find out what happened, and both Smithback and D'Agosta soon find that the answers may be tied to the network of tunnels under the city. The vast population of homeless people down there is being attacked by the "Wrinklers" -- and almost as bad, the dead socialite's mother is stirring up riots against them. 
 To make things even more complicated, Margo Green and Dr. Frock are called on to help identify the second decapitated corpse. This seems pretty normal... until Margo discovers a connection to Mbwun, and a discovery that Frock's theory about where it came from may be entirely wrong. Nightmare fuel and nerd arguments ensue. 
 With everything rapidly going down the tubes, Inspector Pendergast pops up to help D'Agosta contact the underground people, and find out where these Wrinklers are congregating and what they are doing. Unfortunately, they may be running out of time -- the Wrinklers are rising to attack more and more innocent victims, even as the mobs on the surface begin clashing with the homeless. But the true danger of the Wrinklers is more sinister -- and close to home -- than D'Agosta or Pendergast could ever have guessed. 
 "Reliquary" is effectively "Relic Part II: Electrical Skin Boogaloo." While the Mbwun is nowhere to be seen this time around, almost every part of the plot ties into the events of the first book -- the brain-eating, subterranean monsters, DNA weirdness, and the elite world of polish and intellectualism being swamped by musky, blood-spattered brutality. And while Preston and Child had seemingly explained away Mbwun's existence in the past book, they add some interesting twists to this creature's true nature in this one. 
 And as such, Preston and Child give the story the same sort of appeal -- a dark, pulpy popcorn thriller with plenty of blood and harrowing chase scenes in dark tunnels. Despite this, the story is actually rather complex, with two or three investigations going on at the same time before twining together by the climax, as well as a spattering of smaller subplots that wind through them like the roots of a clinging plant. This story also feels grimier and dirtier than the one before it, with lots of explorations down into dark, dank tunnels full of filth and scuttling creatures. 
 They also explore what has happened to the protagonists in the months since the attack of Mbwun. Pendergast seems relatively unchanged (a sort of twentieth-century Sherlock Holmes, down to the disguises), but D'Agosta and Margo seem haunted by what has happened, with Margo learning to use a gun and exercising... you know, just in case. And the ones who have benefited from the event -- Smithback and Frock -- seem to be spinning in opposite directions, with Smithbeck exploiting the whole scenario for all he can, and Frock becoming more arrogant and dictatorial. 
 The biggest problem is perhaps the whole issue of the homeless people being attacked by the wealthy elite, who want to get rid of them... well, because otherwise the world just isn't safe for the wealthy elite to do drugs and party. The abuse of power by the wealthy is a legitimate and serious issue to address, especially towards a group of people with no resources or power, but in a story about wrinkled brain-eating monsters lurking in the subways... it feels shoehorned in, and sometimes it clutters an otherwise lean story. 
 It's bogged down by one too many subplots, but "Reliquary" is a fairly entertaining follow-up to the "Jaws in a museum" tale that came before it, adding some new horrifying twists and shocking reveals to a seemingly simple monster story. Just don't expect the rest of the Agent Pendergast series to have this sort of stuff.