Cell apoptosis. As far as I've been able to find out, the purpose of Apotoxin-4869 was to be a weapon that killed without leaving any trace behind. [He frowns unhappily, although not without some dark humor.] Except when they forced me to take it, it didn't work. Instead it reverted everything except my mind.

Maybe a little more than a year, if I count the time on the train.

[He says all of this in a very clinical and businesslike fashion.]