While in the latest episode, it showed Drew to be the voice, I feel it's a red herring. We never saw Drew actually call Alex and the terrorist knows how to use different voices while contacting Alex and the others. If he could use multiple voices, surely he could just one. I've seen theories it's Fletcher, as we never see him in present day and the phone call he had in the latest episode wasn't from his mom.
What do you guys think?