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