No, just tell the doctor the truth himself.

Shaking his head, John knew he couldn't go this far with Louise. If that meant the doctor knowing that she was his little sister, and the encounter they'd shared that morning, so be it. In fact, he'd save her the trouble and just tell Doctor Harper himself.

'No, doctor.' He glanced at Louise, who had already begun to show her rage that he'd refused. 'The truth is, Louise is my...'

Before he was able to finish the confession, Louise jumped forward and planted her lips on his. He froze, unsure of what exactly was happening, until he felt her tongue probing into his slightly open mouth. She kissed him, opening her own lips into his, multiple times before he somewhat realised what she was doing; trying to silence him. Louise had been bluffing; she didn't want the doctor knowing their true relationship.

She finally pulled back from the kiss, licking her lips with the taste of John's saliva. She smiled at him sheepishly, knowing he'd realised she had bluffed, and hoping the kiss had been enough to keep him silent.

'Uh, if you two need another moment, I can wait,' Doctor Harper said, beginning to get confused.

'John,' Louise said, trying to put on her best little sister voice. 'Should we do what the doctor asked, now?' She raised her eyebrows expectantly.