The key to solving the case is the deceased's girlfriend, Tracy, who had reported the death to the police and calls Rebus, worried about her safety. Tracy, however, raises as many issues as she resolves, adding an element of personal involvement to the investigation.
As the second story in what turns into an evolving series, like the stories in A Good Hanging, Hide and Seek sees Rankin exploring the possibilities of his character, and while the pieces are starting to fall into place, they're not quite there yet and the story doesn't work as well as some of the later volumes, which, I guess, underlines the value of reading (or re-reading) the series in order.
According to Ian Rankin, he set Tooth and Nail in London because that's where he was living at the time, but I'd tend to put the third Rebus story down to a bit more trying out the character to see what works. Given his supposed expertise in the modus operandi of serial killers (as per Knots and Crosses) Rebus finds himself temporarily relocated to London as part of the investigation into a series of killings attributed to the Wolfman.
The change of location allows him to reconnect with his ex-wife and daughter, and Rebus isn't particularly happy about what he finds. That particular subplot is enough to keep him busy while the Wolfman investigation grinds along, but the big story, a particularly brutal series of killings takes its name from the fact that the first body was found in Wolf Street and the murderer takes a bite from each body.
Rebus' presence on the ground in London and his disregard for some of the niceties of protocol doesn't go down that well with his colleagues at Scotland Yard. Neither are they overly impressed by a profile of the Wolfman by an attractive lady psychologist, who isn't quite what she presents as in the course of the cat and mouse investigation into a killer who's a few steps ahead of the police and fairly skilled when it comes to not leaving clues behind.
While there are a few formulaic touches, Tooth and Nail was an entertaining read with the regular ingredients of the series in place even if the setting is different. If there's a weakness, it lies in the ending, a frantic chase scene through the streets of London that seems ultra-formulaic, but it's hard to see how Rankin could have tied up the plot's loose ends without it.