Watch Back to the Future Part III (1990) HD Full Movie Free on SolarMovie. Watch Back to the Future Part III (1990) online free. Stranded in 1955, Marty McFly learns about the death of Doc Brown in 1885 and must travel back in ti...Stranded in 1955, Marty McFly learns about the death of Doc Brown in 1885 and must travel back in time to save him. With no fuel readily available for the DeLorean, the two must figure how to escape the Old West before Emmett is murdered.