At this stage in her brilliant career, it appears that Tess Gerritsen keeps getting better and better. Convincing evidence in support of this statement can be found in THE MEPHISTO CLUB, the latest installment in her hugely popular series featuring Boston medical examiner Maura Isles and Detective Jane Rizzoli. While Gerritsen's signatory elements are all present and accounted for --- an engrossing murder mystery, romantic entanglements and exotic scenery --- she continues to throw changeups into the mix, so that the only accurate prediction longtime readers of her work can make is that something unpredictable will happen.

True to the past form of other books in the series, THE MEPHISTO CLUB is indeed unpredictable, with seemingly every page containing the unexpected. The first inkling demonstrating that all is not right is a gruesome Christmas Eve murder loaded with enigmatic symbolism that brings a ritualistic, even satanic, pall upon the scene. Isles and Rizzoli are brought together once again to work on it, even as they are both distracted by personal issues. Isles, who has in the past successfully resisted acting upon her feelings for Father Daniel Brophy, finds herself continuing to be irresistibly attracted to him in spite of herself. Meanwhile, Rizzoli is shocked to learn that her parents, after decades in a solid, enduring marriage, are having problems --- and she is even more surprised when she finds out the reason.

Isles and Rizzoli, however, must focus on their investigation. There appears to be another murder victim with ties to the case, but the individual in question has yet to be discovered. Matters take on an even greater urgency when two more murders occur, both of which are obviously tied in with the first and one of which claims an investigating officer as the victim. The team suddenly receives some unexpected --- and initially unwelcome --- assistance from a shadowy group known as The Mephisto Foundation. Led by Anthony Sansone, an enigmatic, extremely wealthy patron, this foundation has pursued evil in its multiple personifications throughout history. Rizzoli, despite herself, begins accepting the help and resources that Sansone offers, as his organization always seems to be a step or two ahead of her own investigation.

Meanwhile, a young woman who perhaps holds the answers to at least some of the questions concerning the multiple murders is running for her life through Italy, pursued by an unseen, homicidal madman who apparently has limitless resources --- and her only hope of survival may well lie with The Mephisto Foundation.

You won't find any revolving heads or glowing eyes in THE MEPHISTO CLUB; in fact, Gerritsen maintains an ambiguity regarding the presence (or non-existence) of the supernatural on either side. There is, however, a subtle shift in focus away from Rizzoli and Isles and toward Sansone and his mysterious organization. If Gerritsen's intent with THE MEPHISTO CLUB is to create a fan base in a second, ongoing series, then she certainly will succeed.