Martin and Louisa go to London for his keynote address at the Imperial College Obstetrics Conference. All does not go smoothly: Martin is accidentally headbutted while saving a choking woman, and then his ex-flame Sophie causes a scene at the reception. Back in Portwenn, Penhale proves to be both a hindrance and a help to Janice as she babysits. Guest starring Hermione Norris (Cold Feet, Luther).