When "Stranger Things" season 1 implied Matthew Modine's Dr. Martin Brenner was killed off-screen by a demogorgon, anyone and everyone remotely familiar with the clichés of the horror genre didn't buy it for a second. Sure enough, Eleven's (Millie Bobby Brown) insidious "Papa" resurfaced in season 4, a little banged-up but otherwise no worse for wear and back to controlling his "daughter" under the guise of helping her regain her powers.The dynamic between Eleven and Dr.