A man who lived with up to eight flatmates in a cramped western Sydney share house kept a 15-year-old girl captive for four weeks and allegedly raped her at least four times.

Yet not one of Rashadul Islam's housemates in the run-down bungalow on Balmoral Street, Blacktown, noticed anything amiss as he allegedly held the girl against her will until she managed to escape last Thursday.

The house in Blacktown where the girl was allegedly held captive for four weeks. Credit:Rachel Olding

Neighbours were woken by the girl's screams at 1.30am on Thursday.

A passing police car then saw her running barefoot down Balmoral Street with Mr Islam, 29, chasing behind her.