At the monastery in Shrewsbury in 1138, the gardens are flourishing under the expert tending of Brother Cadfael. His workshop boasts all sort of medication for every kind of ailment. Then one Gervase Bonel, who had planned to leave his valuable manor house to the Abbey in exchange for a house run by the monks where his comfort will be guaranteed for life, is poisoned with Cadfael's own concoction intended for aching joints. As the monk investigates he finds a web of family intrigue, where suspicion has fallen on someone he is certain is innocent.