The 33-year-old man was arrested in Church Warsop, Nottinghamshire, on suspicion of the murder of Freda, 86, and the attempted murder of her husband Ken, 88.
He remains in police custody at this time.
Freda and Ken were found at their home in Station Road, Langwith Junction by a concerned neighbour at 9am on the morning of Saturday 15 January.
Freda was pronounced dead at the scene, while Ken was rushed to hospital where he remains in a critical condition with life-threatening injuries.
Since Saturday detectives have been trawling CCTV and conducting house-to-house enquiries to find those responsible in the days since.
Assistant Chief Constable Dave Kirby said: “Today’s arrest is clearly a significant breakthrough in the case but the investigation continues into this most appalling crime.
“Yesterday (19 January) we appealed for people who were on Station Road between 4.30pm on Friday 14 and 9am Saturday 15 to come forward as a matter of urgency.
“That request still remains – so if you were on that street, either on foot or in a car, then please contact us as soon as possible.”
