An ambulance brings in 79-year-old Mary, who is extremely unwell and until bloods come back, Doctor Jake Mullen doesn't know what treatment she'll need. Consultant Dave Walker orders 56-year-old Steven straight to resus. He has a heart rate of 200 beats per minute, more than double the normal. There is also the case of a 12-year-old who has been attacked by her auntie's pet snake