A woman held a syringe to the neck of a German visitor to Sussex and threatened to stab him.
The 36-year-old victim was approached in Sillwood Street, Brighton, just before midnight on Sunday.
The woman demanded money but he pushed her away and she ran off.
Five minutes later a woman snatched £20 from a 29-year-old Spaniard as he withdrew cash from the NatWest dispenser in nearby Western Road.
Police think the same woman was responsible for both offences and believe she may have been a drug user.
She was about 30 with blonde hair and had blood on her face and clothes. At one point she was seen with a man and another woman.
Anyone with information should contact Detective Constable Weston on 0845 6070999.
Comments: Our rules
We want our comments to be a lively and valuable part of our community - a place where readers can debate and engage with the most important local issues. The ability to comment on our stories is a privilege, not a right, however, and that privilege may be withdrawn if it is abused or misused.
Please report any comments that break our rules.
Read the rules hereComments are closed on this article