Episode 4 of Grey's Anatomy Season 3 kicks off with a surprising reveal. This time it involves Callie's (Sara Ramirez) girlfriend, who unexpectedly turns out to be Penny (Jessica Capshaw).

That was announced during a dinner party thrown by Amelia (Caterina Scorsone). Penny's and Callie's developments do not sit well with Arizona (Jessica Capshaw), who has had a prior relationship with Callie. We find her in a moment where she turns to a glassful of liquid courage to deal with the situation. But, Meredith may very well be the one who is more surprised.

Hence, the budding romance may be headed for trouble because there is a past incident linking Penny with Meredith (Ellen Pompeo). As it turns out, new lover Penny is responsible for Derek's (Patrick Dempsey) death after botching his care. In fact, Derek would have otherwise survived. Unfortunately, she has to be the one to face Meredith again. Naturally, Penny is still suffering from guilt about events in the past.

Meanwhile, the hospital is going through a "silver flood" where elderly patients are coming in by the scores after a bus accident. The veteran doctors task the rookies with notifying families of patients who have died. Owen (Kevin McKidd) is apparently not up to the task of preparing the juniors. So, Meredith steps up with telling them about how to do this properly. She is more than qualified to say this considering the darkness she went through in the aftermath of Derrick's unfortunate passing.

Later on, Meredith gets the opportunity to meet with Penny again. One would expect Meredith to be unforgivingly cold. In a surprising twist thought, she tells Penny to be a better doctor instead.

Other highlights include April (Sara Drew) declining Jackson's (Jesse Williams) request for divorce. Stephanie (Jerrika Hinton) finds herself getting very sick after spending large amounts of time caring for Rachel, a patient recovering from brain surgery.

It turns out that Stephanie was not lying about being anemic and having sickle cell. Jo (Camilla Luddington) thinks Stephanie is lying, and decides to do the "right thing" by going forward to Amelia. However, Amelia discovers Stephanie is telling the truth all along, but only after the former approaches Webber. For awhile, viewers were being led to believe that Stephanie may be a pathological liar.

In other areas of romance, Maggie (Kelly McCreary) and intern Andrew (Giacomo Giannioti) are hooking up.

Grey's Anatomy airs Thursday evenings at 8/7c on ABC.