Sherlock Holmes (Ian McKellen) returns from Japan, where, in search of a plant with powerful restorative qualities, he has witnessed the devastation of nuclear warfare. Now in his remote seaside farmhouse Holmes faces the end of his days tending to his bees with only the company of his housekeeper (Linney) and her young son, Roger. Grappling with the diminishing powers of his mind, Holmes comes to rely upon the boy as he revisits an unsolved case which forced him into retirement, and searches for answers to the mysteries of life and love - before it's too late.