Police have appealed for people who passed by a house where a woman was found with fatal stab wounds to come forward.
Officers were called to Argyle Street, Boston, on Thursday afternoon and found the injured woman, 36. She later died at Boston Pilgrim Hospital.
A man, 47, who was also found with stab wounds at the property, is in a stable condition in hospital.
A 45-year-old man has been arrested and is also being treated for injuries.
Police are treating the death as murder.
Officers want drivers and pedestrians, who were walking between Ingram Road, Laughton Road and Argyle Street between 1355 and 1420 BST on Thursday, to contact them.