You can't take back the things you've done, you can only choose to do what's right to fix them. Following Alex finding Andrew DeLuca and Jo together at their apartment — and beating him to within inches of life — Alex comes in with DeLuca to the ER. After finding out what happened, Meredith covers for Alex, showing he is still her person no matter how many times he screws up or starts going back to his old ways. Meredith knows he has changed, but when Maggie finds out that she was covering for Alex, it tests the trust of their sisterhood.
When Alex tries to apologize to DeLuca, DeLuca becomes scared for his life and starts to panic. Alex feels so badly and knows that he can't take back what he did, so he turns himself in to the police to show everyone that he has changed. Meredith has to apologize to Maggie for keeping it from her that she knew what Alex had done all along. She broke the trust of her sister, but now knows that having another sister is rare, and she must do everything to make it right.
This episode is so pivotal because we see a side of Alex that proves he has become a better man thanks to Jo. With her by his side, "evil spawn" is no more. It also shows that Meredith has learned so much from her loss, you don't get many chances with the people that you love, they can leave you at any moment. Cherish the time you have with them while you have it, and don't let anything get in the way.
