You set out to your loving girlfriend Emma

You tell Emma that you need to have some upcoming work travel - you'll just be gone for one night, but you tell her to behave while you're gone.

The next week when your supposed travel date comes up you go through the motions of packing and making a big deal of saying goodby to Emma. You text her throughout your trip and give her updates to make it feel very real. As far as she knows you're hundreds of miles away from her.

Meanwhile Emma takes the opportunity to go out to a chick flick with Sophia and Isabella. You stalk Emma's movements through a mixture of monitoring her credit card statement, the information she sends to you in her texts, and the show times you can see online.

Emma gets home around 11 at night and sits down to watch an episode of Masters of Sex before going to bed.

You know this because you're watching Emma from a window.

You're wearing all black - new clothes you bought just for this special occasion - including a black balaclava over your head. You're holding rope and a hammer.