The film follows narcotics detective Franz Buloff as he investigates a drug ring and hires a hitman, Max Lindt, to kill his wife, Lisa, suspecting her involvement.

Lisa Buloff is dressed in black, including a veil, attending a funeral for an unspecified deceased loved one.

Weeks earlier, Willie Zoll is at a bar, prepared to share information with Inspector Franz Buloff, the lead investigator in the Hamburg narcotics department for Interpol, about the major drug world target Harry Scheurermann.

However, as Zoll turns into an alley, he is fatally stabbed by an unknown assailant, leaving behind the murder weapon and a dime-store disguise.

He questions why she didn't answer the phone, and when he doubts her explanation of sleeping, she bitterly retorts that she was expecting him to suspect something.

Under the threat of false detainment, Marianne reveals information about Ursula Stein, who picked up a package for her boyfriend, Kurt Mueller, a target of the drug ring.

Mueller is found alive by the police, and Buloff gets a break when he finds Lindt's lucky dollar at the crime scene.

Buloff investigates a red Porsche linked to Lisa and confronts Lindt's friend, Eric Scheurer, at a funfair.

Lisa's friend, Irini von Klaus, owns the red Porsche, leading Buloff to intervene when he discovers Lindt's plan.

[4] was shown in Germany as Das Geheimnis der jungen Witwe (translation: Mystery of the Young Widow).

of Variety described the film as an "okay programmer" and that "Massimo Dallamano's direction [...] is as sturdy as script, on which he also collabed, will permit, and color camera work by Angelo Lotti is particularly effective.