As Watson falls in love and Sherlock Holmes battles his darker habits, the two men once again tackle a case of baffling complexity.

The greatest detective of them all is back... 'Down the Strand the lamps were but misty splotches of diffused light which threw a feeble circular glimmer upon the slimy pavement'. Whilst the seamy streets of London drown in a sea of smog Sherlock Holmes sinks into a cocaine-induced melancholy, until Miss Mary Morstan presents him with a most intriguing case, leading Holmes into an epic pursuit of the truth...