Spoorloos (international title The vanishing) 1988 dutch film directed by George Sluizer.

Based on the novel Het Gouden Ei ("The Golden Egg") by Tim Krabbé.

Rex and Saskia, a couple of young lovers, are on vacation.
They stop at a crowded gas station and Saskia is kidnapped.
After three years with no news from Saskia, Rex begins receiving letters from her kidnapper.

If you've never seen it, it's highly recommended.

The same director will direct the American remake in 1993 entitled The vanishing.

The American Criterion bluray released in 2014 is excellent, English, Dutch and French languages ​​and English subtitles.

The extras:

New 4K digital restoration, with uncompressed monaural soundtrack on the Blu-ray
New interview with director George Sluizer
New interview with actor Johanna ter Steege
Trailer
PLUS: An essay by critic Scott Foundas