I could play a mean game of "Clue." My weapon's the castor bean, my crime site the garden. Easy enough: This member of the Euphorbia clan, which can get 15 feet tall, is about as toxic as a plant can be. Every part is poisonous, but especially the seed. When you hear the cliche that every plant has a story, you'd never imagine it could really involve murder. But in 1978, it did. Bulgarian dissident Georgi Markov was killed by a poison dart filled with ricin, the main toxin found in the castor bean, that was fired from an umbrella. Markov, a Communist defector working for the BBC, had just left his office and walked across Waterloo Bridge to start his journey home. He was waiting at a bus stop, felt a sharp stab in his thigh and saw a man picking up an umbrella, according to CNN. He developed a high fever and was dead four days later. The assassin has never been found but the KGB is suspected. Wow! Who knew. A friend gave me this castor bean plant which bears a striking resemblance to marijuana, though of course you'd have to look that up because you wouldn't know what THAT looks like. For all its toxicity, which recommends it to terrorists and other seekers of potent biological weapons, this is a truly beautiful plant. It lives, temporarily, in a giant space left by the removal of some steroidal ornamental grasses that should never have gone in there. (I'm sworn off Miscanthus forever.) So it won't last the winter. I do hope the various critters that skulk around back there stay away. I'd hate to have to bury the evidence.