Der Dolch des Batu Khan (2004)

Widower Peter Schwarz tries to be a good dad for Sebastain 'Basti', but his work as museum curator in Dresden keeps taking priority. Even Basti's 12th birthday, supposed to be crowned by a quality time trip, takes second seat when a treasure stolen during Word War II from Saxony's king August the Strong's fabulous collection is found. A museum employee in cahoots with art thieves steals the priceless dagger of Genghis Khan's heir. Basti finds clues, but dad is still too busy, even flirting an employee, who also takes to Basti. So the boy snoops with his best friend Benni.