As Nacho Vigalondo’s new film “Colossal” opens, a gigantic beast with skin that looks like tree bark has suddenly materialized over Seoul, South Korea. After a night of drinking, Gloria (Anne Hathaway) awakens to news coverage on the scores of Koreans who have perished under the creature’s attack. Horrified, she notices one extra hitch: the monster’s actions exactly mimic her own — everything from phone tossing to dancing. It turns out, if she does it, then so does the creature.

The film begins with Gloria breaking up with and getting evicted by her boyfriend Tim (Dan Stevens) because of her incessant lies regarding her drinking habits. Lacking money and a home, Gloria moves back to her childhood abode, which is inexplicably empty and unattended to. Back in her hometown, she swears to Tim she’ll get her life in order — until her plans quickly run amok when she runs into her old friend Oscar (Jason Sudeikis) who happens to own a bar. Needless to say, more drinking than life-organizing ensues.

It’s during these binge-drinking sessions when the unnamed Kaiju monster first appears, and a simple allegory is established — Gloria’s internal demons of alcoholism are manifested physically in the monster. This concept is fitting and joyfully toyed with throughout the film’s first hour. Hathaway plays up the absurdity of having a monster-double, drunkenly relishing in the ability to make it gyrate here and there, which works as a tremendously bizarre yet entertaining visual gag. The actress also grounds the absurdity in solemnity as she emotionally elaborates on how her movements can have very dire and disastrous effects.

It then seems that “Colossal” would progress into a narrative simply about confronting one’s personal issues, which would have worked just fine. The concept of the film is original and wondrous enough to justify such a straightforward story. Instead, the film takes a turn for the peculiar, as Oscar discovers he has his own Kaiju, a robot. While his demons are introduced — at one point we get a glimpse of his disgustingly cluttered home — “Colossal” instead reaches for a commentary on male privilege.

There’s just one issue — the film’s second-half turn makes no logical sense within the story’s progression. Much of the issue lies in Oscar’s characterization in the first half, as he’s a nice, unassuming dude whom anyone would want to grab a beer with — typical fare for Sudeikis. However, there isn’t a whiff of the insecurity, sadism or controlling behavior in Oscar’s nice-guy persona that’s needed to justify his sudden character change — upon which he becomes remarkably cruel.

Sudeikis portrays both halves of Oscar convincingly, suggesting that Vigalondo’s writing is to blame for the fact that his character — and the movie — make essentially no sense. This point is furthered by the fact that the film doesn’t dedicate much time to explaining the reasons behind Gloria’s alcoholism — a very half-baked explanation with a career in journalism is vaguely offered — nor does it work to truly address the issue. The origin of the monsters is neglected as well, relying on a supernatural event that has no explanation and chemistry between Gloria and Oscar as children that simply isn’t there.

“Colossal” sadly has two halves that just don’t add up, resulting in a film with too many of its own issues to overcome.

“Colossal” opens in theaters this Friday.

A version of this article appeared in the Monday, April 3 print issue.

Email Ethan Sapienza at [email protected].