Severus rematerialized just outside the gates to the Greengrass estate, thankfully he'd chosen to Disillusion himself before he'd Disapparated from the Malfoys', a precaution he'd taken to using whenever he was uncertain of the circumstances of his destination.
Moving quickly, he disabled the wards easily and unlocked the gates, slipping through and replacing the wards. It wouldn't do to have anything seem out of place to anyone on the outside. Striding across the lawns, he murmured "Homenum revelio." A quick glance told him what he wanted to know. One person in an upper floor room at the back of the house, likely a bedroom, and another alone in a room overlooking the approach to the house. His instincts told him this was where he needed to go.
Another murmured spell later, and he was swirling once more into the darkness of Apparition.