Sometimes — “Phone Booth,” “Cellular” — they pay him the big bucks for it. More often, than not, however, he goes the low-budget route — “Maniac Cop,” “Q,” “The Stuff” — and the result can be gold. Or at least well-polished fool’s gold.

Such it is with 1990’s “The Ambulance,” a spirited conspiracy thriller about an unauthorized vehicle that swoops up diabetics and takes them to an unknown locale for devious reasons. Janine Turner, before she got really famous on the series “Northern Exposure,” is the first victim, collapsing on the street whilst being hit on by Josh Baker (Eric Roberts, rocking a major mullet), an artist for Marvel Comics. (And, yes, geeks, Stan Lee is in it and plays himself.)

As she’s being wheeled in to the ambulance, Josh tells this beautiful stranger he’ll visit her in the hospital later, but when he does, there’s no record of her being admitted. Because he’s apparently that desperate and hard-up for female companionship in a city teeming with millions, he takes it upon himself to unravel this mystery. Eventually aiding him are an old-school journalist (comedian Red Buttons) and a frizzy-haired cop who’s not bad-looking herself (Megan Gallagher) so why’s he wasting his time and risking his life over the sick one?

Although a thriller, “The Ambulance” has its tongue planted firmly in cheek, as all the Cohen greats do. It’s never showy about it, nor does it appear as parody, but it carries a lightweight touch as it goes through the genre’s conventions of danger and derring-do. Casting soap star Eric Braeden as the movie’s “special guest” is just one move indicative of Cohen’s slyness as an independent filmmaker.

Roberts is quite the surprise here. I hadn’t seen the film since it first was dumped unceremoniously onto VHS, so I did not recall how “into it” he is here, proving himself a rather able comedian with a fair amount of motor-mouthed charm. With him setting the pace, and Cohen keeping up in the action department, the film flies by at the speed of its phantom emergency vehicle. —Rod Lott

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