The Drowned Boy by Karin Fossum

When 16-month-old Tommy is found dead in the pond behind his house, Inspector Sejer and his partner, Jacob Skarre, have a hard time believing that it was an accident. Tommy's mother, Carmen, is acting especially strangely. while his father, Nicolai, seems overwhelmed in grief. Tommy also had Down's syndrome and it was not a secret that Carmen was put out by that fact. Are the detectives correct in their suspicions and, if so, will they be able to find sufficient evidence--or will someone get away with murder?