Unlike their spring 2018 fashion collection, Kate and Laura Mulleavy’s first foray into moviemaking, “Woodshock,” is depressingly dull and terminally inarticulate.

Oh, it’s pretty enough, in the superficially embellished style of a perfume ad or fashion video — the gifted Finnish cinematographer Peter Flinckenberg virtually empties his bag of tricks. But it’s more lacking in substance than a yard of silk chiffon.

The title refers to the psychological panic engendered by being lost in a forest (here played by the giant redwoods in Humboldt County), but Theresa (Kirsten Dunst) isn’t physically disoriented, just mentally unmoored. Having helped her sick mother die using a spiked spliff, Theresa, who works in a medical-marijuana dispensary, descends into a detached reverie of hallucinatory grief. Neither her boyfriend (Joe Cole, underemployed to the point of effacement) nor her boss (a miscast Pilou Asbaek) can reach her.

What follows is less a consideration of the fallout from an act of euthanasia than a succession of disjointed, dreamlike scenes of Theresa listlessly caressing tree trunks and her mother’s shabby-chic furnishings.

More than one person will die as she continues to mope and medicate, attired in a succession of lace-trimmed chemises. Yet no substantive conversation or hint of greater meaning pierces this gauzy void, which the Mulleavy sisters, whose fashion label is Rodarte, decorate by slapping butterflies or flowers on virtually every available surface.

Filmmaking might be a natural sidestep for fashion designers — as Tom Ford has twice proven — but “Woodshock” is a painterly bore.