"Only Mama Knows" is the fourth episode of the eleventh season of Grey's Anatomy and the 224th produced episode of the series. It is also the 335th produced episode of the Grey's Anatomy franchise. It was broadcast on Octobter 16, 2014.
In an attempt to reconsile the discover of her half-sister, Meredith goes searching through her mother's diaries and old video footage as both she and Richard find themselves dealing with their memories of Ellis Grey. Meredith attempts to piece together the parts of her childhood she can't remember, including her mother's suicide attempt and pregnancy, while Richard grapples with the consequences of the decisions he made during his residency, all while cautiously avoiding Maggie. Meanwhile, Meredith's refusal to confide in Derek the truth about her half-sister further fuels their fight while Maggie drops a bombshell when she resigns from Grey Sloan Memorial, prompting new board member Bailey into action in order to keep her on the staff. Elsewhere, Alex is dejected to learn that the board vote wasn't as contentious as Arizona led him to believe while Arizona continues to struggle balancing her role as department head and her fellowship.
- "This is how my mother wanted to be remembered. My memory of her is a little bit different. I'm sure everyone remembers their own versions of her. Versions I wouldn't recognise. But that's the tricky thing, nobody's memory is perfect or complete. We jumble things up, we lose track of time, we're in one place then another and it all feels like one long, inescapable moment. It's just like my mother used to say; the carousel never stops turning."
- "They say we can repress our memories. I wonder if we're just keeping them safe somewhere because, no matter how painful they are, they are our most valuable possessions. They made us who we are. "
This episode's title originated from the song Only Mama Knows, originally sung by Paul McCartney.
- Although creditited, Sara Ramírez (Callie) and Sarah Drew (April) do not appear in this episode.
- This episode features stock footage of Ellis' interactions with Meredith and Richard from the episodes "Shake Your Groove Thing", "Make Me Lose Control", "Wishin' And Hopin'" and "I Must Have Lost It On The Wind"