A Study In Sable: The Elemental Masters by Mercedes Lackey
One of ten novels in the series that looks at Dr.John Watson, who is an Elemental Master of water and takes the sort of occult cases his dear friend, Sherlock Holmes refuses to even consider. Though Holmes appears uninterested with the occult and those cases, he does vet Nan and Sarah for him as he wants to work with them on difficult or near impossible cases. Nan is a psychic, while Sarah is a medium and together with their birds, Neville the raven and Grey the parrot, they are four of the most talented investigators around. They even surprise Watson and Holmes with their skills and use of their talents.
