The props are central to the final scene of the now-globally-notorious staging of Mozart's Idomeneo by director Hans Neuenfels for the German opera house. In that scene, the title character, the newly abdicated King of Crete, carries onstage a bag containing the four severed heads and places each one on a chair.
(Poseidon is the only one of the four unfortunate divines who actually figures in the opera's plot.)
There were some protests by offended Muslims when the Deutsche Oper last presented this Idomeneo in 2004. This past September, with Christian/Muslim relations in Europe much more tense than two years earlier, the opera house cancelled performances of the production scheduled for November, citing concern for the safety of cast, crew and patrons following a warning from Berlin authorities of some unspecified threat involving the staging.
Neuenfels said that the final scene, an addition of his which is nowhere in Mozart's original, was his own protest against all forms of organized religion; he refused to let it be cut.
Once the cancellation was announced publicly, a huge row broke out within Germany over freedom of artistic expression and censorship, with even German federal Chancellor Angela Merkel saying publicly that "self-censorship out of fear is not tolerable." (Questions of good taste and voluntary forbearance loomed smaller.) There was worldwide media coverage of the argument; police subsequently changed their minds about the danger involved, and the Deutsche Oper rescheduled two performances of the production for December 18 and 29.
Now that the items that provided the occasion for all the fuss have disappeared, media interest is naturally high. But the company doubts that the heads were stolen or destroyed: spokesperson Alexander Busche told the AP that a production staff member had recently seen them and that they were probably tucked away somewhere in the house's workshops. "The costume director and the technical director are having a look around, but if they don't turn up, we'll just make new ones," he said. "What matters for us is that we have heads on the 18th."
Perhaps understandably, the Deutsche Oper's employees have gone a bit out of their own heads over the brouhaha surrounding this production. "I will be so happy when this Idomeneo is over," "We would really like to get back to just promoting and staging normal opera."