[Benji_]

Spoiler:

the nominated housemates were asked for how little amount of money they would leave the house. Big Brother told the housemates that the housemate with the lowest amount will be evicted. However, that housemate will gain immunity from eviction and replace him- or herself with either Gina or Sophie. As Dexter was the housemate with the lowest amount of money, he is immune from eviction and chose Sophie as his replacement.