Derbyshire Police said a man had been arrested in Warsop in the early hours of today on suspicion of the murder of Freda Walker and attempted murder of her husband Kenneth.
Freda, aged 86, and 88-year-old Ken were found at their home on Station Road, Langwith, by a concerned neighbour at 9am on Saturday.
Freda was pronounced dead at the scene, while Ken, a serving member of Shirebrook Town Council and former Bolsover councillor, was rushed to hospital, where he remains in a critical condition with life-threatening injuries.
Derbyshire Police said a 33-year-old man had been arrested in Warsop today. He remains in police custody at this time.
And police officers were later seen searching a property in Church Warsop.
Assistant Chief Constable Dave Kirby, of Derbyshire Police, said: “Today’s arrest is clearly a significant breakthrough in the case.
“It comes from a lot of help and support from this community, and I would just like to say thank you to everyone who has helped us so far.
“Yes, we have made an arrest, but of course, the investigation carries on, so we're always looking to add to the information that we've got.
“One of the leading lines of inquiry is it may have been a burglary and that remains a leading line of inquiry.
“The man was arrested in the early hours and, as you would expect, there will be interviews and so on, and if we can give any more information about motive then we will do, but at this time we can’t be conclusive.
“We can't rule out the involvement of anybody else, but at the moment we are focusing our inquiries on this particular man we've arrested.
"As soon as we can update, particularly if the community are worried about any potential further risk to them about whether there might be somebody else, then we will give that update.
Anyone who may be able to help detectives with their enquiries is asked to contact Derbyshire police on 101, quoting reference 240-150122.