After his restaurant goes bankrupt, Lin Yuanzhou returns to Baijiao Island to handle his ancestral home, only to discover a tidal pool in the North Cliff sea cave that connects to the year 1988. On the other side of the tidal pool is his grandfather, Lin Shouchao, when he was young. Learning from old records that his grandfather will go missing in a storm forty-nine days later, Lin Yuanzhou uses thirty-eight years of separation to pass clues back and forth, learn seafood gathering, repair the lighthouse, and investigate the truth behind the long-misunderstood shipwreck. In the end, they not only rescue the people at sea but also bring three generations of fractured family affection back with the tide.