The caller was David Kneale, the company's newly appointed chief commercial officer. And the news he bore was truly staggering.
Mother, long regarded as the rank outsider and thought to be in the contest only at the behest of Boots' ousted marketing chief, Ann Francke, had beaten some of the most powerful names in UK advertising to be named lead agency on the Boots business.
Even as Mother was saying a Christmas thank-you to its 80 staff by treating them to a long weekend on the ski slopes of Val D'Isere, its senior managers had hardly hoped they could pull off such a coup.
Sure, the Mother-led agency alliance had confidence in itself. It had even chosen to pitch under the collective name of Los Galacticos after the circle of superstars playing for Real Madrid.
What's more, it felt it had built up a sufficiently large body of support within Boots to withstand the effect of Francke's departure.
It had certainly done enough to make it through to last week's penalty shoot-out, head-to-head with the incumbent, J. Walter Thompson.
Nevertheless, the Mother camp was worried that WPP's Sir Martin Sorrell would save the business for his JWT subsidiary by offering an irresistible financial deal allied to WPP's co-ordination capacity.
It didn't happen. But then nothing has gone according to the script in this pitch.
Unwisely, in restrospect, Francke set the pitch wheels in motion soon after her appointment as the director of strategic marketing at the beginning of the year.
The chain's ills were obvious: the company had failed to define what it stood for, its 1,470 stores were dated, its products expensive and supermarkets were stealing its business.
Francke sounded out two senior agency managers she knew well, Stef Calcraft, one of Mother's founding partners, and Andrew Robertson, BBDO's North American chief, with whom Francke had worked when she was in charge of pan-European petfood marketing at Mars.
Francke indicated that she was looking to review the business, but thought it fair to give JWT a chance.
But her decision to call such a review before Richard Baker's arrival as chief executive astonished the industry.
The appointment of the one-time Asda marketing director ensured that Publicis, with which he had previously worked and which had extensive retail experience, would be added to the pitchlist.
It also sealed Francke's fate. "It wasn't a personality clash, only that Baker wanted a leaner structure at board level," an industry source said.
Another added: "It was a tough decision but the right one. Baker wanted retailing and marketing working hand-in-hand and Francke's role was redundant as he saw it."
Now, however, "the re-sult completely vindicates Francke", a source close to the pitch said.
"Three strong networks pitched and Mother has seen them off."
January: Boots hires the former Mars petfood marketer Ann Francke as director of strategic marketing.
April: Francke instigates wide-ranging review of Boots marketing.
May: Boots announces that Richard Baker, Asda's chief operating officer, will take over as chief executive in September.
July: Boots revealed to be preparing to review its £44 million creative at J. Walter Thompson, threatening WPP's global tenure of the business.
September: Boots invites JWT to contest its business along with Mother, Abbott Mead Vickers BBDO and Publicis. Each will lead a consortium of agencies.
October: Francke ousted. Her responsibilities are given to David Kneale, the chief operating officer, who becomes chief commercial officer.The review continues.
December: Shortlist is reduced to Mother and JWT. Mother then awarded the business.