They spotted three masked men outside the house on a residential cul-de-sac in the Bailiff Bridge area at about 4.42am yesterday (Sunday).
They were looking at cars on the drive and one of the men broke in through the front door, threatened them with a knife and demanded keys to three cars outside.
The suspects, all wearing dark clothes and balaclavas, made off empty handed when the couple said the police had been called.
Acting Det Insp Toby Facey of Calderdale CID, said: “This was a serious offence in which the victims were threatened at knife point in their own home, in what must have been a very frightening experience.
“We are continuing to support them and are conducting a number of enquiries into what took place."
He added that officers want to speak to anyone who has information or who witnessed any vehicles or males travelling on Bradford Road towards Hell Fire crossroads or towards Brighouse at around the time of the offence.
Contact DC 6276 Holly Douglas at Calderdale CID on 101 referencing crime number 13180267318 or Crimestoppers on 0800 555 111.