The O'Shaughnessy sisters, Mary and Pamela, have been writing collectively under the pen name "Perri O'Shaughnessy" for a good while now, building a voluminous mythos around Nina Reilly, a professionally talented but personally troubled attorney who has a penchant for attracting danger even while eschewing it. CASE OF LIES, which may turn out to be the penultimate novel in the series, finds Reilly changing residential locales yet again, relocating this time to Lake Tahoe, Nevada, yet continuing to find that the problems of her past affect her present and future.

O'Shaughnessy brings quite an interesting mix into CASE OF LIES, with a group of MIT students, one of whom is a bona fide mathematical genius on the verge of solving one of the world's greatest puzzles. The students hit the Tahoe casinos with the goal of busting the tables by utilizing a card-counting scheme based upon --- what else? --- mathematical probability. It works fine until they are robbed; and, in the course of the robbery, a pregnant woman who is an innocent bystander is killed.

Flash forward to the present: Nina Reilly is brought in at the eleventh hour to represent Dave Hanna, a somewhat reluctant plaintiff in a wrongful death suit. Hanna is the husband and father of the woman and unborn child murdered during the course of the robbery. The students are the only witnesses, and they seem to have vanished into the sands of time. The statute of limitations to bring the matter to trial is running, and with Hanna's original counsel withdrawing, Reilly has little to work with.

With some dogged investigative work, Reilly is able to trace the mathematics student. It's pretty ingenious the way this is set up --- so ingenious, in fact, that it smacks of a real-world incident. Reilly's involvement in the case, however, seems to have drawn the murderer out of the woodwork, and almost immediately he seems to be after Reilly and everyone else connected to the case.

Mathematics plays a big role in the backstory of CASE OF LIES, and O'Shaughnessy does an impressive job of introducing the reader to the history and world of numbers, and those who are obsessed with them, without capsizing the plot and the entire book along with it. Some of the mathematical concepts presented herein are a bit dense, and those of us whose idea of calculation is knowing in advance how much to pay the pizza delivery guy could have gotten lost pretty quickly were we in lesser hands. But O'Shaughnessy pulls this really neat trick wherein she equates an element of quantum physics with some basic (and understandable) legal concepts and makes everything --- if not perfectly clear --- clear enough.

CASE OF LIES isn't all prime numbers and quantum theorem. Far from it. There's a passel of interesting characters, a bit of sex and explosions (even taking place simultaneously at one point), and an extremely well-explained plot that is just complex enough to be interesting and, given the math tie-in, quite exotic. A side trip to Germany to depose witnesses on the run also gives Reilly a chance to reestablish an old and unresolved link with an old flame. And there also is a particular moment two-thirds of the way through that will bring you out of your seat.

Given that it may be a while before we see another Nina Reilly novel, CASE OF LIES is a must-read this summer.