Boris Johnson has less than a month to go as Britain’s prime minister. Two candidates are trying to convince Conservative voters in the UK that they’re the right ones to fill his shoes. Who are they and what do they stand for? Also, in today's show, The World concludes its series looking at how wars end. Plus, Serena Williams announced this week that she is stepping away from professional tennis. And, a global dance movement for people with physical disabilities is filling theaters, getting TV time and spawning international competitions.