Fans of "Grey's Anatomy" will experience a throwback of sorts as Meredith (Ellen Pompeo) and Derek's (Patrick Dempsey) first meeting is mentioned in episode 4 of the show's 12th season as Maggie apparently follows her sister's footsteps. But personal problems aside, the sisters will encounter a bigger problem when they forget about a dinner party they are supposed to host. 

Things got very emotional in this season's third episode. In "I Choose You," Alex was forced to choose which of two newborn twins he'd be operating on as he could only do one liver transplant. Meredith also had to make a choice regarding her new contract's much lower salary. Meanwhile, her sister Maggie (Kelly McCreary) freaked out when she received a wedding invitation from her ex-boyfriend and ended up sleeping with a new intern, Andrew (Giacomo Gianniotti). 

This little slip-up will follow Maggie well into episode 4, "Old Time Rock and Roll," as a teaser for the episode shows the two discovered by Amelia (Caterina Scorsone). Maggie also appears to be mortified that she slept with an intern and bemoans the fact to her sister, Meredith, asking who would even screw an intern. 

"The father of my children" was Meredith's playful reply, referencing the time she and Derek ended up sleeping together after they met at a bar. 

And like her sister, who endured several awkward encounters with the erstwhile McDreamy afterwards, Maggie will also have a number of awkward encounters with Andrew as she tries to avoid him; even hiding behind Meredith as a last resort. 

However, interns are the least of the sisters' worries as they forget to organize a dinner party that they are supposedly throwing for everybody. 

The interns will also have a trying time as Owen (Kevin McKidd) tries to teach the new doctors how to talk to the families of their patients, especially when the news they have to share isn't good. 

On a more uplifting note, Arizona's (Jessica Capshaw) 90-year-old patient will reportedly give her hope about finding love again. 

Episode 4 of "Grey's Anatomy" season 12 is set to air on Oct. 15.