The National Gallery in London has flooded, and senior curator Quentin Lester has a dramatic solution. He proposes that the entire collection of priceless paintings should be removed from London and stored in an abandoned slate mine inside a Welsh mountain, as they were during the Second World War. Soon after Quentin is settled in North Wales admittedly more at home in a cave among his paintings than he is with other people he unwittingly sets in motion a series of events that wake up this sleepy, charming town. After mistaking local boy Dylan Hughes for an art history genius, Quentin finds himself in the middle of mayhem.