If nothing else, Alien: Covenant is the most ambitious Alien film ever made. It's almost as if Ridley Scott, foiled in his recent attempts at biblical epics, metaphysical dramas and thorny psychosexual thrillers, decided to revisit those genres under cover of a prized franchise sequel. Which isn't to suggest that this latest Alien entry (the sixth in the series proper, not counting assorted spin-off confrontations against the Predator) short-shrifts the monster-movie hysterics: There's plenty of screaming and running and gore here -- much of it effective, some not. Really, though, what shines through most are the Ridley Scott-isms.

As a ship of colonists faces an alien outbreak, Scott masterfully orchestrates the initial pandemonium: Scattered crew members struggle with poor communications, ion storms, blood-vomiting colleagues and an escalating cascade of cock-ups. We are constantly reminded that these aren't soldiers; often, when these people try to help, they make things worse. Covenant could have continued in this vein and delivered a perfectly serviceable action-horror sequel. But Scott has bigger plans. He wants to do so much here: Probe the nature of faith and the mysteries of creation, examine the limits of humanity and intelligence, compare visions of leadership and devotion.

The effect is that of a film at war with itself -- between philosophical ambition and the need to deliver an effective action spectacle. Admittedly, the whipsawing between the lofty and the base, between cerebral musings and visceral thrills, generates its own wild energy -- at least until the disposable and thoroughly uninspiring action-movie theatrics of the final act.