Police launched a murder investigation after a man of 80 was found unconscious in his car.
The elderly man was arrested on suspicion of murder after he was discovered at the wheel of his vehicle in Keighley Road, Colne, on Saturday evening.
On Sunday morning police found the body of a 76-year-old woman, believed to be his wife, in a house in Ivy Bank Lane, Haworth.
A post-mortem has been carried out on the woman, but the cause of death is still to be established.
The man is in custody. He was taken from his car to Airedale General Hospital where doctors say he is in a serious but “stable” condition.
Anyone with any information that could assist West Yorkshire Police enquiries is asked to contact the Homicide and Major Enquiry Team on the non-emergency number 101, or to ring Crimestoppers on 0800 555 111.