Group sex

Freud's sexual constitution was not exclusively masculine after all, to "hunt in couples" means sharing one's gratification with someone of one's own sex. *
* Jones, Ernest, Sigmund Freud: Life and Work: The Formative Years and the Great Discoveries, 1856-1900, (1953, p. 11).

In The Psychopathology of Everyday Life (1914), Freud's own, Freud described an alleged conversation, fake, of course, that he never had with, a young man of academic education, thus, without a doubt, his lover, Wilhelm Fliess. As Freud revealed, the young man was conversant with some of my works, which proves that the man was Fliess. At the time, Freud hardly managed to sell a few copies of his greatest (fake) work, The Interpretation of Dreams. In the year 1900, when the psychopathological book was published, very few people, besides Fliess, knew that Freud even existed, let alone what works he had written.

The conversation is rather long, but the crux of the matter was, according to Fliess, too intimate ... to impart.
In the fake conversation, Freud was acting as the detective, who could figure out what hid behind a slip of the tongue committed by Fliess.
So what was on Fliess' mind? Well, he confessed, I suddenly thought of a woman from whom I could easily get a message that would be very annoying to us both.

So, there was a woman involved with both Freud and Fliess. And there could be an annoying message related to both of the two villains, partners in crime. As the plot thickens, it shouldn't be difficult for an average person to figure out what kind of annoying message a woman could send, especially taking into account that Freud liked, sharing [his] gratification with someone of one's own sex. In other words, Freud liked ménage à trois in all its forms. As it is apparent, in this case, Freud shared the woman with his bisexual boyfriend, Fliess.

Freud wasn't hiding what the message would be about, revealing that Fliess feared that she missed her courses; not good news to either of the partners in crime. After all, this was about having sex with a patient, not about love or marriage, and babies weren't welcome.
Funnily, Freud claimed that Fliess told him that the lady is Italian (1), a play on words, an often repeated Freudian joke; Freud always enjoyed word plays. As he explained in the dream book: In German, gen Italien [stands for to Italy], and when joined, it becomes Genitalien [genitals]. (2). So this is what Freud was intimating; the fact that together with Fliess, without any contraceptive protection, they both had sex with a woman [visited the woman's genitalia (Gen-Italien)], and now they were in trouble.
In my view, the woman in question was Emma Eckstein, who, as recounted on the page titled Killing Freud's fetus, was subjected to an abortion performed by Fliess, assisted by Freud and his wife. It always surprised me that Fliess would come to Vienna to perform an abortion on one of Freud's patients, Emma, without a charge. He wasn't even a gynaecologist, so why would he even attempt this task? And the answer is in Freud's allusions in the psychopathological book. Since not only Freud but also Fliess had unprotected sex with the women, either of them could have been the father. Neither Freud, nor Fliess, wanted a child out of wedlock. So, Fliess came, and killed the unborn baby, and almost killed the mother.

Sharing a woman for one's sexual satisfaction, as in this case, can have some unexpected and unpleasant consequences.

(1) Freud, Sigmund, The Psychopathology of Everyday LIfe, (1914, pp. 17 ff.).

(2) SE 4, p. 232.