'Grey's Anatomy': Derek Shepherd's Mother, Sisters Return During Amelia-Centric Episode

Grey's Anatomy brought back two memorable guest stars during Amelia's big family reunion episode.

"Good Shepherd" saw the neurosurgeon travel to New York with Link (Chris Carmack) to operate on a patient with a serious spinal deformity.

The pair, who recently became romantically involved, hoped to have a quiet romantic getaway together, but things took an unexpected turn after Amelia's (Caterina Scorsone) sister Nancy (Embeth Davidtz) invited them to dinner at her home... after she mistakenly believed Link was Owen (Kevin McKidd).

Wanting to avoid the awkwardness of explaining the end of her relationship with Owen, Amelia and Link go to Nancy's home ready to keep the lie alive.

"Kathleen is the worst. Kathleen is like Martha Stewart if Martha Stewart also had a license to diagnose you with a personality disorder," Amelia says to Link before they get to Nancy's.

Things began to unravel after her sister, Kathleen (Amy Acker), turned out to be a surprise guest, who also had no idea Amelia was in town.

"I guess I'll put the wine away," Kathleen says, throwing a dig at Amelia's addiction problems.

Nancy admits she didn't mean to stage a family reunion, though she did reveal Liz (Neve Campbell) could not come because she was out of town. Nancy also admitted she did not tell her mother about the meal.

Though the dinner started with some awkward moments, by dessert it seemed the event would go smoothly, until their mother, Carolyn (Tyne Daly) arrived by surprise to all three sisters' dismay. Her arrival ruined Amelia's lies, since she met Owen when she first visited Derek back in Season 5.

After the sisters found out the truth — including her past brain tumor — they began to attack Amelia by bringing up all of her past transgressions. Link comes to her defense in an attempt to advocate for her, accidentally revealing her situation with Betty and Baby Leo.

The drama led to an abrupt end to the dinner, and Amelia their new relationship might not work because now he "knows too much" about her. Their conversation was interrupted after their patient started to crash and they had to rush to the hospital.

After successfully performing the difficult surgery, Amelia tried to apologize to Link for being harsh before but he walks away saying he needs time to think. Amelia then ran into her mom and the pair shared a heart-to-heart where Carolyn admitted she is the one who is most like her late father.

Grey's Anatomy fans have not seen Nancy since she made her debut in Season 3. When she paid a surprise visit to Derek (Patrick Dempsey) while he attempted to make his failed marriage to Addison (Kate Walsh) work. Derek's mom Carolyn was introduced in Season 5 when she paid the hospital a visit and first met Meredith (Ellen Pompeo).

The Shepherd family reunion also marks the first time the sisters reunited onscreen since Derek's death.

Grey's Anatomy airs Thursdays at 8 p.m. ET on ABC.