John Tadsen is a fictional character portrayed by Mark Jacoby in the TV series The Blacklist.
They appear in 1 episodes out of a total of 218 aired
Episodes1
The Apothecary (No. 59)
episode S4.E15 february 2017Red has to figure out who betrayed him when he's poisoned; Liz and the task force look for the toxin's designer to save Red's life.
