Final answer:
The question does not provide specific details, but the Harrisons would typically leave phone numbers where they can be reached, instructions on pet care, and what to do in case of an emergency when leaving a house sitter like Spencer for the evening.
Step-by-step explanation:
The type of information that the Harrisons gave Spencer when they left for the evening is not specified in the question you have asked. However, in the most common situations similar to this, it is typical for homeowners to provide house sitters with a range of important information.
Typically, this might include A) Phone numbers of the places they would be, in case the house sitter needs to reach them urgently. They would also likely leave instructions on B) what to feed Muffy, if Muffy is a pet in their care. Lastly, they would provide guidelines on C) what to do in case of an emergency, which might include contact information for emergency services or specific instructions about the house and pet care in such situations.
For a house sitter or someone taking care of a pet, it is always essential to have this information to ensure everything is managed well in the homeowners' absence.