In reply to Chris the Tall: that explains the reason why sam and alex were aware of their existence in the real world, but to be honest the device with the stopped clock and Gene's reference to Molly just after this revelation lead me to believe that Alex had died at this time.
another thing which confuses me and anyone who knows please enlighen me...
Sam's mentor appeared in 1973, younger than same policeman who died of a heart attack in 2006(?) whereas everyone else went back exactly the same age
Gene was supposed to have died in 1952, how can he have physically been there to take Alex Drake's hand after the death of her parents in 1981 if he did not exist in reality at that time?