One: One grain of sand with one drop of blood goes ignored by attackers, figuring they’re close enough to shore that the tide will wash away evidence.

Two: Two weeks since the missing report, two detectives get the lab results for one fleck of blood on one grain of sand, found by pure luck.

Three: Three suspects in three separate rooms won’t get their stories straight. They won’t know why it took the two detectives two weeks to bring them in. They won’t know what the lab had to say about one fleck of blood on one grain of sand.