Actress Ellen Pompeo, of the series "Grey's Anatomy," arrives at the 2013 People's Choice Awards in Los Angeles, January 9, 2013.
Actress Ellen Pompeo, of the series "Grey's Anatomy," arrives at the 2013 People's Choice Awards in Los Angeles, January 9, 2013. Reuters/Danny Moloshok

“Grey’s Anatomy” Season 12 does not have a new episode this week. Episode 21 (“You're Gonna Need Someone on Your Side”) will air on April 28 on ABC. Here is a review of some of the developing stories in the medical drama.

Spoiler alert: This update contains “Grey’s Anatomy” Season 12 spoilers. Details include a quick recap of Greys 12x20 (“It's Alright, Ma (I'm Only Bleeding”) which aired on April 14.

Arizona (Jessica Capshaw) finds out that her ex-wife Callie (Sara Ramirez) is moving to New York to be with Penny (Samantha Sloyan). She reacts fast, talks to a lawyer and decides she will fight for custody of Sofia.

Arizona’s battle means Calzona, a fan-favourite couple in Grey Sloan Memorial, is headed for another potentially disastrous phase. This time, though, the fight is about a baby. Will Callie even try to throw in her face that Sofia’s only other parent is the late Mark Sloan (Eric Dane)? Fans hope not. Arizona has been as real as a mom could get to Sofia, even after their divorce.

Amelia (Caterina Scorsone) and Owen (Kevin McKidd) are sticking to a boring pattern of exploring romantic ties, breaking up and trying again. It has been going for so long. Series creator Shonda Rhimes and her Shondaland writers may have grown so comfortable doing it without realizing just how predictable these two have become. This time, Meredith (Ellen Pompeo) is stepping in to help resolve the issue, according to the ABC synopsis of “Grey’s Anatomy” Season 12, Episode 21.

Meredith herself has a romantic issue to deal with in “Grey’s Anatomy” Season 12. Can she now move on, two years after Derek (Patrick Dempsey) died? Meredith sleeps with Dr Thorpe (Scott Elrod) and freaks out like a trauma patient the morning after. They clear the situation soon after that, with Dr Thorpe saying he is willing to wait until she is truly ready to move on.

In Greys 12x20, Jackson Avery (Jesse) and April Kepner (Sarah Drew) find themselves in a state of truce after Avery delivered a seemingly heartfelt speech, reminding Kepner that they were best friends protecting each other when they were still in-love. Soon after, they feel their baby kick for the first time.

“Grey’s Anatomy” Season 12 has characters reeling from all sorts of conflict, making it a force that is still alive as a medical drama. Despite its imperfections (and even after the departure of Sandra Oh’s Cristina Yang), viewers keep coming back if only to check out the latest developments in one or two of their favourite characters or couples.

“Grey’s Anatomy” Season 12 airs Thursdays on ABC.