You should only read this question if you already saw the movie or are not afraid of spoilers. I cannot formulate this question without giving away crucial parts of the plot.
In the a scene between Walter and David we see that
they fight, probably until one of them will be dead.
We later know for a fact that
David survived the battle, as he enters the covenant pretending to be Walter.
The question that comes to my mind is: (sorry, again spoilered)
Did David kill Walter or convince Walter to let David go, continuing with his experiments?
The motivation for this question comes here:
During their fight we see that Walter soon controls David on the ground and prepares to land the killing blow but is hesitant to do so. While on the ground David distracts Walter by asking him to choose between them (i.e. humans) or his brother (i.e. androids) while reaching for a knife. The outcome, at least to me, remains unknown. Did David stab Walter, killing or at least disabling him, or did Walter let go?