Her cousin Solomon, who lives with Catherine and her family, is a practicing Jew, a fact the family chooses to keep secret, especially in light of the recent cries of heresy. One group of heretics particularly troubling local authorities is a band of hermits let by Eon. Among the group is Cecile who has escaped from a cruel master and is hiding. The son of Catherine's good friend, the abbess Heloise, Astrolabe is also among the group. When Cecile is found murdered, Astrolabe stands accused and turns to Catherine, whom he knows to be sensible, to protect him and help him find who murdered Cecile and who wants him to hang for the crime.

Conveniently, because of an epidemic Catherine is taking her two young children to Heloise's convent to escape the plague. Catherine's husband Edgar and Solomon follow close behind them on their way to Spain to do some trading. This makes a perfect cover for Astrolabe to travel to see his mother and for Catherine to uncover the truth about Cecile's murder.

Heresy, as with earlier Catherine LeVendeur mysteries, is successful in two ways. First, the ease with which the twelfth century is described is such that it allows the reader not to concentrate on period details and awkward, unfamiliar speech patterns, but allows full emersion into the complex and engrossing mystery. Secondly, because the period is described so well that a great sense of time and place is achieved with little effort.

Catherine is fiercely loyal and protective of her family and instills similar values in those around her. Though her last baby died in infancy and she and Edgar still grieve, they do not allow their grief to rule their lives, nor do they allow fear for their unborn child to dictate their actions.

Those tentative about reading historical mysteries will find this series a very approachable place to begin. Catherine is a very strong heroine without being foolhardy and the mystery is engrossing. Paired with a detailed setting that brings twelfth century Paris to life, this is another strong entry into a fine series.

--Jennifer Monahan Winberrry