A woman has been found with stab wounds outside a house on fire.
Two young children were also discovered inside the house suffering from smoke inhalation, Sussex Police said.
Emergency services were called to the address in Worth Road, Pound Hill, Crawley, just after 0630 GMT on Tuesday.
A spokesman for Sussex Police said the woman had been taken to Crawley Hospital for treatment.
The children were taken to the New East Surrey Hospital, where they were treated for smoke inhalation.
"Police are treating both the injuries to the woman and the cause of the fire as suspicious," the spokesman said.
"A man has been arrested and is currently helping the police with their inquiries."