Black cat with no markings. Partner and I visiting his parents from London. She was at home with us but one of the windows was very slightly open at top floor (3rd floor). We’ve previously had no issues as she’s quite timid of jumping from heights so didn’t think too much. Currently cannot find her in the house and wonder if she’s managed to jump out! We definitely didn’t see or hear anything of the sort and checked garden, but just in case!