That enigma always
reminds me of that time when Batman went missing for several
weeks, after a brutal fight against the Joker and his henchmen
(and his henchwoman). The Joker had hidden in a dangerous
industrial area, and during a confrontation with Batman and
his allies, a member of Joker's gang caused a massive explosion
that left nothing of Batman but his cape and cowl.
The Police and Batman's friends investigated
to find out who killed the Dark Knight, but with no success.