Dakota Fanning as Sara, Daniel Brühl as Kreizler
Sara (Dakota Fanning) finds out that Kreizler (Daniel Brühl) has been lying about his malformed arm in Season 1, episode 6 of TNT’s “The Alienist.” TNT/Kata Vermes

Sara learns something mysterious about Kreizler in the next episode of “The Alienist.”

According to the synopsis for Season 1, episode 6 of the TNT series, Sara (Dakota Fanning) looks into Kreizler’s (Daniel Brühl) past. And in a sneak peek from the hour, Sara shares what she found out about the criminal psychologist with John Moore (Luke Evans).

“I was thinking about my father which got me to thinking about Kreizler’s theory about fathers, which got me to thinking about Kreizler’s own father,” Sara tells John.

When John asks if she’s looking for something on Kreizler’s father, Sara points out that she’s actually looking for something about Kreizler himself.

“You seemed to be obsessed with the man,” Kreizler comments. “Perhaps you’re in love with him?”

“Perhaps I am,” Sara answers casually.

She then admits that she didn’t know what she was looking for at first. “But when I saw this, it struck me,” Sara continues before handing John an old newspaper clipping.

After Sara told John to skip down to the second to the last paragraph of the article, John reads, “The evening was highlighted by young master Kreizler who dazzled all with his interpretation of Mozart’s Concerto for Piano No. 20 in D Minor.”

When John says that he didn’t see “anything unsettling about a piano recital,” Sara tells him that Mozart’s Concerto for Piano No. 20 in D Minor “cannot be played by one hand,” so Kreizler has been lying about his malformed arm, which he’s been claiming to be a congenital defect.

Also in the episode, John checks in on a friend. While it’s unclear who this friend is, a promo photo for the episode suggests that it’s one of the boy sex workers he met while investigating the string of murders in the city. In the trailer for the hour, John informs his friend of the possible day the serial killer strikes next.

Elsewhere in the episode, the team hatches a plan to catch the killer, as Kreizler faces his own self-doubt about the investigation. Meanwhile, Roosevelt (Brian Geraghty) attends an event with the city’s elite. And former police captain Connor (David Wilmot) acts on impulse.

“The Alienist” Season 1, episode 6, titled “Ascension,” airs on Monday, Feb. 26 at 9 p.m. EST on TNT.