A married couple in their 70s are recovering in hospital after being stabbed on their doorstep in Lewes.
Sussex Police said the couple had answered the door to a woman in Hawkenbury Way just after 1500 BST when they were attacked.
Officers said the the woman stabbed the couple "a number of times" before she was restrained by the man.
A 59-year-old woman was arrested at the scene and is being questioned in custody in Eastbourne.
A force spokesman said the man suffered a broken ankle and the woman has stab wounds, which are not believed to be life-threatening.
He said the motive for the attack was unclear and appealed for witnesses to come forward.