Il coltello di ghiaccio (Detrás del silencio)

Il coltello di ghiaccio (literally Knife of Ice) is an Italian-Spanish giallo that Umberto Lenzi directed in 1972; he also co-wrote it. Shot in Italian, it runs 92 minutes and is known as Le Couteau de glace in France and Detrás del silencio in Spain. Carroll Baker, Evelyn Stewart and George Rigaud lead. Stewart, who also worked as Ida Galli, like Baker appeared in several other Lenzi films.

A mute young woman falls into danger when a serial killer begins to stalk the Spanish countryside. Unable to describe what she has seen, she is left isolated as fear and suspicion close in. The cast also includes Luca Sportelli, Franco Fantasia, Lorenzo Robledo, Eduardo Fajardo and Ágata Lys.

The title comes from a line attributed to Edgar Allan Poe that likens fear to a knife of ice piercing the senses down to the depths of conscience. The line was not Poe's but an invention of the filmmakers. The picture was the fourth and last collaboration between Baker and Lenzi, after So Sweet... So Perverse, Orgasmo and A Quiet Place to Kill. Elements of the script and direction recall the work of fellow Italian director Lucio Fulci, and the critic Robert Firsching wrote that it should prove fascinating to genre devotees.