Calum, 41, was last seen at around 1.45pm on Thursday, November 7 in the Dalmore area of Alness, Ross and Cromarty.
We told how he did not turn up for tea with his parents on Thursday afternoon, who then raised the alarm.
Officers have established that Calum visited the Morrisons store on Dalmore Road at 1.27pm.
He bought food items then walked out of the supermarket.
Coastguard, RNLI, Mountain Rescue Teams and the local community are helping police with their search.
Calum is described as white, 6 ft, stocky build, bald and was wearing a black jacket with a blue logo, black trousers jeans, light blue shirt and black boots.
Inspector Alasdair Goskirk said: “We are continuing to work to establish Calum’s movements from when he was last seen and would ask that members of the public review the CCTV images to see if they recall seeing Callum.
“The images show the clothing we believe Calum to be wearing when he was last seen, which are a black jacket, a light blue shirt, black jeans and black boots.
“It has now been over four days since Calum has last been in contact, or seen, his family.
“They, along with officers, are understandably worried for his safety.
“We’d continue to appeal to anyone who has seen Callum, or has any information on his current whereabouts, to contact police as soon as possible.”
Those with information are asked to contact Alness Police Station via 101, quoting incident number 3129 of Friday, November 8.