slimy and disgust alien invade earth . they attach themselves to people back and control their mind . sam nivens ( eric thal ) and father andrew nivens ( donald sutherland ) and mary sefton ( julie warner ) be all part of separate government agency who join together to fight the invasion . not a faithful adaptation of heinlein book but still a good film in it own right . the script be good while it have realistic and believable character while the alien be agreeably disgust and the action scene be good and violent . also and with the sole exception of sutherland ( who appear to be sleepwalk ) all the acting be good especially thal ( tall and handsome and hunky ) and warner ( beautiful and intelligent and strong ) . a very good sci fi film . also and i agree with some previous poster one of the best scene in the film be thal nude shower scene . woof .