Soon Lord Grantham's yellow lab Isis would meet her demise. Old age had worked its weathering wiles on its test subject: spraining joints and implanting stomach tumors. If the dog were to pass before Robert, there would be no cheering his soul and his fierce character would fast become intolerable to all whom resided at Downton from the cooks to the maids to his noble daughters and wife. Henceforth there existed a single solution, the furball must not expire.
Mr. Joseph Moseley, butler at Downton, knew this to be true. He had just recently attempted to color his grey worn-down, straw mop a bold black. This fashionable exploit had caused Lord Robert to question Mr. Moseley's lineage, and he asked if he were descended from those of Italian blood. Of course, how could Lord Robert possibly comprehend the truth behind this cover-up? No one at the great house would ever in one million years venture a guess at Mr. Moseley's true identity: a cunning time traveller from two hundred years on in the future.
His hair then had reached its balding, greyed state following years of harsh time voyaging, which had slowly cast its battered toll upon his visage. Unassuming and bumbling, Mr. Moseley easily fit in at Downton as he had read of this past time in school texts of his own time and thus understood how to appropriate himself to this time's customs and cultural norms. And if Mr. Moseley knew anything from his time venturing through the space-time continuum, he knew of the importance of love.
It was unconditional and devoted love that Lord Robert felt towards his elderly pup. And so the loss of this feeling would reap only destruction and discontent throughout the house and thus cast a negative light on the remainder of Mr. Moseley's data collection there as a time analyst, a curator of the past in future times for the British Museum. And so it went that this mysteriously gifted and knowledgeable Butler concocted a plan to time-hop his way back to his present time to collect a vial of "pixie dust", an enriching formula which would allow Isis's cells to regenerate and thus halt the aging process and heal her. The night upon which this occurred coincidentally happened to be Christmas Eve.
That evening, Moseley dusted off the ancient looking trunk that he kept hidden underneath his bed at his home in town. He then proceeded to unlock this mysterious bit of luggage with a key he kept fastened around his neck with a worn, frayed black velvet chord. Inside there existed a remote of sorts with a single button. Moseley pressed the button with his right thumb and his body disappeared in a flash, reappearing in his home in the future in his pharmaceutical room where he hastily grabbed for the "pixie dust" before pressing the button once more, appearing once again in the past.
Moseley could not afford to linger there in his future, his true present as any indication of his present deception in his past existence would be too much for him to bear. He could not fathom a future in which his present love of the past Phyllis Baxter existed no more. Moseley, back in Downton times, patted down his waistcoat with purpose, removing the ashy residue created via his travelling and placed the vial of regenerating powder into his chest pocket.
That holiday feast, Isis's lamb chop would be seasoned with a dusting of the future's goodwill. The dog, appearing much more spry and slightly following its lifesaving repast, quickly and cheerily sought out its master. Robert, noticing his canine companion's changed state, elected for his Christmas wish to be that Isis keep on living as happily as she appeared now. And thanks to Mr. Moseley, she did.