For hundreds of years, romantic relationships in western society have been based on the idea of monogamy: two people, together, for ever. But with nearly half of all US marriages ending in divorce, perhaps the traditional model is no longer fit for purpose. In Love Without Limits, Louis travels to Portland, Oregon, the heart of a movement seeking to rewrite the rulebook on how we conduct intimate relationships and experience family life. Portland, whose city motto is 'Keep Portland Weird', is seen as the US capital of polyamory and ethical non-monogamy, the practice of openly and transparently having multiple relationships that go further than just sex. Louis embeds himself with families who have made the bold decision to open up their relationships in a number of different ways, whether inviting others into existing relationships or allowing partners to seek romance elsewhere. He discovers that for many, more partners means more love and more happiness. But for others, multiple relationships have led to jealousy, upset and broken hearts.

Louis Theroux spends time with those preparing to take a lethal but legally prescribed overdose and meets a controversial group educating others in how to end their lives.

Louis Theroux explores open adoption in California, where women hand over their babies at birth to adoptive families paying tens of thousands of dollars for the privilege.