Warning! SPOILERS for Knives Out ahead.

Knives Out is chock full of great characters, but Great Nana is a surprising standout among the bunch. Directed by Rian Johnson, Knives Out is a murder mystery about the suspicious death of author, Harlan Thrombey. Initially ruled a suicide, it isn’t long before all those present on the night of his death are considered murder suspects - many of whom are members of his own family.

The cast Johnson has assembled for Knives Out is enormous and it includes such high profile talent as Daniel Craig, Jamie Lee Curtis, Chris Evans, Michael Shannon, and Toni Collete. Johnson also managed to cast legendary stage and screen actor, Christoper Plummer as the murder victim. But of them all, it’s actress responsible for Great Nana who gives a scene-stealing performance.

In the role of Wanetta “Great Nana” Thrombey is actress K Callan. In Knives Out, she’s Harlan’s mother - a fact that is both shocking and hilarious since Harlan is celebrating his 85th birthday at the start of the film, and Callan is herself six years younger than Plummer. Still, with some convincing age makeup and a clever performance from Callan, Great Nana is a great and, as it turns out, very important character in Knives Out.

K Callan Plays Great Nana In Knives Out

Knives Out is K Callan’s 24th film, but she’s been working in the industry since 1956. Among her film work are roles in American Gigolo, Frankie and Johnny, and more recently, Tyler Perry’s Why Didn’t I Get Married Too, but it’s largely been in television where Callan has built her career.

Starting out in in the 1962 CBS series, Route 66, Callan has appeared in episodes of several hit shows from across the decades. These include Barney Miller, All in the Family, Newhart, St. Elsewhere, and Quantum Leap, to name only a few. Her biggest TV role is that of Martha Kent on the mid-90s series, Lois & Clark: The New Adventures of Superman. Since then, she’s also had recurring roles on How I Met Your Mother as Lily’s Grandma Lois and most recently in Veep season 5 as Judy Sherman, a congressman’s wife who runs in her dead husband’s place.

Why Great Nana Is So Good In Knives Out

When it comes to her role as Great Nana in Knives Out, Callan is a surprise standout. She plays the astonishingly still-alive Thrombey matriarch in such a way that she’s at first glance easily dismissible, but then her wry amusement at her family’s squabbling makes her impossible to forget. In fact, Callan’s role as Harlan’s mother may not seem like a very important one, but she winds up providing what may be the biggest clue to identifying Ransom as the murderer.

The reveal that Ransom, Harlan’s grandson, is who plotted the murder of his grandfather is only fully explained once Great Nana is questioned by Detective Benoit Blanc (Craig). It is she who provides the missing piece of the puzzle, revealing that Ransom (Evans) did return to the house on the night of the party, sneaking back in the same way Marta (Anna de Armas) does later on. This is why Great Nana, mistaking Marta for Ransom, says, “Ransom, you’re back again?” when she spies Marta through the window. The scene is working on two levels: it’s a joke at the expense of a senile old woman, but it’s also the linchpin in naming Ransom the murderer.

Like the scene itself, Callan is also playing Great Nana on two different levels. On the one hand, she is the old woman who can’t hear and can barely see, that’s why she’s able to mistake Marta for Ransom. But on the other hand, she’s the only person who observes what really happens the night of her son’s murder, suggesting that she isn’t as senile as she seems. In Knives Out, Callan gives a memorable performance that is subtle in its overall importance, but it’s what allows Great Nana to unexpectedly deliver the film’s biggest twist.

Next: Knives Out Real Killer & Ending Explained (In Detail)