Police arrested a man after a body was discovered at a house in a Calderdale village.
Officers were called to the address on Holly View in Triangle, near Sowerby Bridge, at 11pm on Sunday following concerns over the safety of a member of the public.
The body, believed to be that of a man in his 60s, was discovered inside the property.
A post-mortem has since been carried out and detectives say the death is currently being treated as suspicious.
A 28-year-old man has been arrested on suspicion of murder.
Police are appealing to the public and want anyone with any information to call Calderdale CID via 101, quoting incident 1394 of January 22.
Information can also be passed on anonymously to Crimestoppers on 0800 555 111.
In unrelated investigations, police would like to speak to the people pictured in the image gallery below. The people pictured in the images may be witnesses as well as suspects. If you recognise anyone, contact police on 101 quoting the reference number on the image caption.