What is love? Is it the first flush of desperate passion and emotion unleashed when two hearts are first entwined? Is it the steady affection of the long-term couple? Or is it something stranger, less easy to define: the love between two friends, the love between human and object the all-consuming obsession of the stalker the energiser of murder, mayhem and war? Can it span time? Can it span the unthinkable distances of space? Can it span the awful gulf between life and death? Can it be described at all?