Operating on coal and steam energy, Steam City is a metropolis reminiscent of London. The city is often shrouded in mist, providing malevolent characters with a convenient hiding place to carry out their sinister schemes. However, a select few have the courage to venture beyond the mist into the unknown - the Steam Detectives. This team consists of Narutaki, armed with his versatile convertible firearm, his assistant nurse Lingling, and his Megamaton robot Gohliki.