What is the dark thing my client has seen flying around in her home four nights in a row now, and has her large guard dog cowering when he sees it? What needs to be done to remove it?

This is a human lost soul spirit, not a demonic spirit meddler nor an extraterrestrial spirit. It is not wanting to cause harm, but it is in turmoil, confused, and disoriented, being disconnected from normal senses in a kind of hyper-vigilant state wanting to connect with something. Work with the healing protocols is very much in order here because the problem with human spirits is always needing to honor their free will, even when they have misguided notions, confused, disoriented thoughts and sometimes are stuck in a kind of malevolent or hostile mode that is a reaction to having transitioned, but only partly, and now being stuck in limbo. Your advice to your client was quite appropriate because such spirits are seeking human companionship and that could result in spirit attachment to the energy of a living person and be a source of disturbing thoughts and feelings. This frequently confuses the body, having two sources of consciousness on board, not to mention someone else's agenda. We see this as a straightforward healing mission for which your Lightworker Healing Protocol and Deep Subconscious Mind Reset process will be effective. This might take some time needed to raise the vibration of this lost one so it will be able to see and interact with the light callers and cooperate in being guided to the heavenly realm where it needs to go, to continue on its soul journey. So your efforts with the protocols will be the key in bringing that about.