The documentary-maker returns with a new series examining the way the USA is changing. In this opening edition, \u201cLove Without Limits\u201d, Theroux travels to Portland, Oregon, where some people are experimenting with different kinds of relationships. With nearly half of all marriages in the country ending in divorce, Portland is the centre of a growing movement where polyamory \u2013 multiple relationships \u2013 are becoming more common. Theroux examines both the positive and negative aspects that such relationships have had in the city. Louis Theroux\u2019s Altered States is on BBC Two at 21.00.