Why did Nancy take Oliver to sikes

What chapter are you referring to? Sikes declares that they must go and find out what happened to the boy, but none of them wants to go anywhere near the police station. Bet and Nancy return, though, so Fagin asks Bet to go. She refuses, as does Nancy, but Sikes ultimately convinces her to go. At the station Nancy asks for her brother Oliver, and the officer tells her that he was taken off by a gentleman to somewhere in Pentonville. Nancy gives this information to Fagin and Sikes, and Fagin sends her and Dodger off to find him.