German police in the western town of Neustadt late Wednesday responded to a possible sexual abuse case, only to walk into an erotic bondage session – which they were then invited to join.

A man called police about possible sexual abuse after he peeped through his neighbor's window to see two men tying up a half-naked woman.

Read more: Sex in Germany: Study opens a window into German bedrooms

Police entered the apartment to investigate, only to learn that the woman was tied up with her consent and without mistreatment. They were able to speak to both the woman and her partner, who police described as "well and in a good mood."

"The tenant of the apartment, a teacher of Japanese Shibari bondage, was instructing a couple in the art of erotic bondage," police said in a press release titled "Fifty Shades of Neustadt."

Neustadt police said the officers were invited to participate in the "training session" but had to "politely" turn down the offer.

German police are regularly called to odd or non-emergency situations.

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