A man armed with a knife attempted to rob a shop and a supermarket in Wrexham on Thursday.
North Wales Police say they believe the same man tried to snatch the contents of a till at Ashfield Stores, Cefn Mawr, and tried again later at the Iceland supermarket.
Officers also want to speak to a witness who tried to stop the man at the supermarket.
The first robbery attempt was made at about 1445 GMT.
The offender jumped over the counter and tried to take money but was unsuccessful and he ran off.
Later in the afternoon police believe the same man attempted to snatch money at the Iceland store in Rhosddu.
The robbery also failed and police are keen to speak to a member of the public who tried to stop the man leaving the shop.
Police say the man is in his late 20s and around 6ft tall.
He was wearing a red cap, grey fleece and jeans.