Holidaying in a small Welsh seaside village in the early 60s, a brother and sister enjoy exploring, until the last day of the holiday, when six year old Daniel disappears without a trace. It seems only Jennie, his five year old sister, knows what happened, but her memories are suppressed for decades - until, as a grandmother, a small pencil box triggers memories. But is what Jennie thinks she remembers what actually happened? Leaving her brother behind, when the tide was coming in, could only mean one thing... and all that was left, was one small red sandal...