S23·E75 Uncut Killer

When three teenagers collapse after taking uncut cocaine, Diane and Sally are sent to visit the school they all attend. There they break up a fight and further investigations reveal the two girls involved are both caught up in the local drugs scene as suppliers. While they investigate a new supply of pure-grace cocaine, Grace makes a momentous decision about her career, Phil drops a bombshell on his Sun Hill colleagues, and Jo decides to take a new step in her love life.