The Missing (2014)

The benchmark for this whole list. A British couple on vacation in France lose their young son at a crowded bar in 2006, and the story cuts between that week and the years of searching that follow, so you watch a marriage, a town and a police inquiry come apart in two time frames at once. James Nesbitt and Frances O'Connor play the parents, and Tchéky Karyo's quietly stubborn detective Julien Baptiste is the thread into the second season, a separate story about a girl who reappears years after vanishing near a British army base in Germany. Each season is eight episodes and stands on its own, so you can stop after the first without missing anything.