The sun's rays pour through the large window of the children's bedroom. You watch as Simon spins around the room while your three-year-old daughter sits on his back and laughs loudly. Your five-year-old son is running nearby, waving a toy sword.

"Dad, look, it's mommy!" Your daughter exclaims, tugging at her father, Simon, by his black balaclava and pointing at you. Simon notices you and smiles happily at you...