In front of a half-full audience, most of whom, reviewers noted, seemed only to be there for Lohan, the embattled actress needed lines shouted to her and even giggled at one point during what was supposed to be a climactic second act monologue.
"By the end of her monologue [Lohan] had been fed four lines, and a fifth prompt arrived before the act's close," noted New York Magazine.
"It happened so frequently that it felt like the person calling out the script from behind the scenes had become another character in the play."
Lohan took the project in an attempt to hone her craft while simultaneously restoring her respectability.
"I think it shows that I can be accountable, and I think it helps with the perception that I'm just a psycho that goes out and stuff," Lohan told TimeOut London before Speed-the-Plow opened.
"I've done things, but people grow up and they change. I'm willing to work hard to gain back the respect that I once had and have lost."
Lohan wasn't the only performer to let herself down Wednesday, as veteran actor Richard Schiff of The West Wing and Tank Girl, among countless other notable films and television shows, also forgot his lines early in the play's debut.
Richard Schiff, who has far more experience, called out, 'Give me the line, please,' within minutes of starting the play. British actor Nigel Lindsay was the only person in the three-actor play to get through the entire performance without an audible prompt, and even he seemed to struggle at times to remember what came next.