Trainee 999 call handler Mackenzie is put to the test when she takes a call from a patient in labour with twins.

A call comes in from London Fire Brigade requesting assistance at a fire in a block of flats which immediately puts the team under pressure. Meanwhile, mother and daughter team Nicola and Maisie have just finished with their first patient of the night but are immediately dispatched to a 12-year-old boy who has had an unfortunate accident.