The million-dollar Mer-Der question may finally get the much-awaited answer in episode 17 of "Grey's Anatomy" season 11 titled "With or Without You." In the last installment of the hit medical drama, a woman answered Derek's phone when Meredith called him. 

The trailer for the upcoming episode reveals that Derek rushes from D.C. to his wife's doorstep to clarify things out. However, Meredith is already convinced that her husband cheated on her so any explanation from him would just be of no value to her. 

While the cheating incident is still up in the air, fans have reason to believe that Derek really is repeating history, this time with his new resident named Renee Collier (Scottie Thompson). The new lady in town is seen holding Derek's hands and making some flirty glances. She also attempts to kiss him but the trailer does not reveal if Derek kisses her back. 

Apart from Meredith, Callie also thinks that Derek is guilty of cheating on his spouse. The orthopedic surgeon sees Derek's sudden homecoming as something to be followed by an apology. Why else would he do that? Callie reasons it is "because he has something to apologize for." 

Carter Matt suggests that his rush to Seattle can also mean that Derek wants to explain what happened. From his side, it may be that he had the urge or he was tempted but did not engage to it. 

Maggie, on the other hand, is convinced that there is an explanation to a woman answering Derek's phone in the middle of the night. She suggests that it was a nurse who picked up the call, maybe because Derek is in the middle of performing a surgery. 

There's no telling who is right and who is wrong. Better catch episode 17 of "Grey's Anatomy" on March 26.