Edward carefully plotted the murder of his enemy. One winter's day he strangled her in the bedroom, then faked a burglary. He ransacked the house, scattered possessions and broke through the patio doors. He set the burglar alarm downstairs before driving to the local golf course to establish his alibi. Two hours later, when Edward was in the middle of his golf game with three colleagues, the burglar alarm went off and the police were alerted. They found the house apparently broken into and the woman strangled. No animals or electrical devices were found which could have set the alarm off, so it looked as though an intruder had set off the alarm before killing the poor woman. Edward was never arrested or charged. The police inspector long suspected Edward, but there was one question which he could not fathom: How did the suspect get the burglar alarm to go off so conveniently? Can you work it out?