By LINDSEY BAHR You can almost smell the sweat in “The Secret Agent,” a stylish, slow burn thriller about radicals and mercenaries in 1977 Brazil. Filmmaker Kleber Mendonça Filho begins his film with the note that it was “a time of mischief.” It’s a sly kind of promise of what’s to come over the next 2 ½ hours, where audiences will meet hit men, zombie legs, corrupt cops, a two-headed cat and a quiet man named Marcelo (Wagner Moura) who is running away from something — and into something possibly more dangerous. The film opens in limited release Wednesday. Death...