"Code Black" is back with episode 4 this week to take you back into the country's busiest ERs. In the last few episodes we saw how the first-year residents are trying hard to cope with the stress at Angels Memorial Hospital and impress their tough-minded residency director Dr Leanne Rorish. And in "Sometimes It's a Zebra" this week, Leanne will have yet another clash.

CLICK HERE to watch episode 4, titled "Sometimes It's a Zebra", live. And CLICK HERE to watch it later online.

In episode 3 we saw how the doctors pull off 36 consecutive hours in "Code Black" and Leanne takes a mental break after this. Mario, on the other hand, pushes Angus to perform a thoracotomy when two brothers are brought in from a MVC enter codes. When the attending get to know this, they are upset and banish him, but Mario doesn't stand-up for Angus.

"Pre-Existing Conditions" also saw the doctors treating the case of MDMA reaction. And Christa handling the case of a prisoner brought in with kidney failure resulting from organ rejection after his transplant.

Leanne is affected by the similarity of the MVC case to her own family and then Jesse is seen comforting her. And at the end of the episode, Jesse and Leann share a moment as they leave the hospital.

This week in episode 4, we will see a new surgical attending Cole Guthrie joining Angels Memorial with the help of his estranged father. He will have a clash with Leanne over their contrasting approaches to medicine. Meanwhile, "Sometimes It's a Zebra" will also see Christa's confidence shaking during a procedure as she handles her first infant patient since the loss of her son.

Plot synopsis of episode 4 reads:

Guthrie's estranged son joins Angels Memorial as a surgical attending; Leanne clashes over their contrasting approaches to medicine. Meanwhile, Christa experiences a crisis of confidence in the middle of a procedure.

"Code Black" episode 4, tilted "Sometimes It's a Zebra", will be aired on CBS on 21 October at 10pm.