One of the keys to John Sandford's success as a serial author is his ability to take us inside the twisted psyches of his villains. Once a protagonist has been established, there's only so much more that can be added in successive books. It's the bad guys, different in each installment, who offer the potential for creating intriguing new characters.

In "Escape Clause," the newest crime thriller featuring detective Virgil Flowers, we're well past the midway point before Sandford puts some oomph into his malefactor. He almost makes up for this with a terrific third act, but by then he's fighting an uphill battle.

It's a typical Sandford work in that the plot starts quickly and moves briskly. It opens with crooks stealing two rare tigers from a zoo with the intention of selling their organs on the black market for traditional Asian medicine.

This is far from a one-man job. It takes planners, henchmen, brokers, exporters and importers. To his credit, Sanford tries to make all of them interesting. But by the time we've met everyone, it's hard to figure out who to focus on — a problem the author seems to wrestle with a bit, too. We end up knowing a little about all of them but not much about anyone in particular.

Adding to the sense of distance is a subplot that doesn't add much except 50 pages. Flowers' girlfriend gets recruited to help with research for a doctoral thesis on how a food processing plant is taking advantage of its low-paid immigrant workforce. It's certainly a topic worth exploring, but we're not exactly talking Upton Sinclair's "The Jungle" here.

There is one saving grace for Sandford fans: He churns out these serial novels with the proclivity of a mini-donut machine. This one is a little undercooked, but there's certain to be another one coming down the line soon.

Jeff Strickler is a writer and editor at the Star Tribune.