An ordinand at a remote clerical college dies suspiciously. His father, a wealthy man, gets Adam Dagliesh involved. Turns out Dagliesh had spent several summers there as a teen. When Dagliesh gets there, there's been a second death. The woman had a bad heart so it seems like she had a heart attack. But Dagliesh finds out the knitting in her hand was held improperly, and she had on the glasses she would have worn to watch TV.

The school is probably going to be closed, but the terms of the Arbuthnot will (the woman who left the college the land and buildings), the money from the property goes to the 4 priests in residence unless a legal heir to her father is found. Another death under Dagliesh's nose and he is right on the trail.

This is where he meets Emma who is there as a guest lecturer.

Dagliesh realizes it was a teacher who was the father of the ordinand. The ordinand was illegitimate and was left at the college and raised there. The dad had married the mom recently before she died, retroactively making the young man a legitimate heir and through mom, set to inherit the college.

Good mystery.