Xtro
(1983)

Annalise is imprisoned in a cabin bathtub, cocooned and impregnated by her now half alien brother's spawn, which she proceeds to spew into the tub at random intrevals.

Joe discovers that Sam may be responsible for the murder of the girl from the begining of the movie.

Joe goes to the cabin to save Rachel, and gets killed when the alien screams at him.

Tony starts to change into an alien too, and Sam takes the boy off in a spaceship leaving Rachel all alone.

Thanks Annie!