Surely the whole point of golf is that it's difficult to know where the ball will go. So it's highly unlikely that, when an errant golf ball hits Matthias Kavanagh in the head causing a fatal riding accident, someone actually intends to kill him. But Sister Agnes Bourdillon can't help thinking that his death is the result of foul play, especially when she learns that another rider was injured in a similar incident only days before.
Reason tells Agnes she's wrong, but as a nun she can't accept that the universe is governed by such cruel randomness. Another death is enough to convince her that a killer is at work. But, consumed by doubts and deserted by those she most depends upon, she'll need to delve deep into her reserves of ingenuity and strength to establish not only the truth about what she's sure is murder, but also the foundations of her own beliefs.