Christmas this year is going to be a little different for the Keller family, as parents, Anne and Ben, buy their three adult children - oldest son, Cal, middle son, Dylan and daughter, Emory - a river cruise down the Danube River from Germany, through Salzburg, to Vienna touring beautiful European Christmas Markets and towns along the way. The one problem? The very different siblings, who are each going through their own personal life challenges, have naturally gone in separate directions over the years and the idea of spending 10 days cooped up on a river cruise together makes each Keller child cringe for their own reasons. But they say "yes" because that's what families do, never expecting it to turn out to be a glorious once-in-a-lifetime experience full of missed connections, new friendships, stunning vistas, relationship upheaval, budding romances, shipboard games, family bonding, and a secret that brings them all together in time for Christmas.