In the waning months of the second World War, a group of children discover an earthen tunnel in their neighborhood. Throughout the summer of 1944--until one father forbids it--the subterranean space becomes their "secret garden," where the friends play games and tell stories. Six decades later, beneath a house on the same land, construction workers uncover a tin box containing two skeletal hands, one male and one female. As the discovery makes national news, the friends come together once again, to recall their days in the tunnel for the detective investigating the case. Is the truth buried among these aging friends and memories? This impromptu reunion causes long-simmering feelings to bubble to the surface. Mild-mannered Alan, stuck in a passionless marriage, begins flirting with Daphne, a glamorous widow who was once his teenage sweetheart. Michael, lonely after the death of his wife, considers contacting his estranged father, who sent Michael to live with an aunt after his mother vanished in 1944. Lewis begins remembering details about his Uncle James, an army private who once accompanied the children into the tunnels, and who later disappeared.