There's a part of him that's annoyed by John's endless attempts to capture his attention that doesn't want to find this case interesting, just on principle. However, as he talks, his attention is caught, interest piqued. It's still fairly simple - how many possibilities are there? Someone's been killing people or at least supplying them with rope, or else security is highly lax in several institutions, which is statistically improbable. Most likely is that it's hospital staff...

...his mind is already whirring with possible connections, just from that. Still, he tries to come off as though he's not terribly impressed. Which lasts for all of thirty seconds. He finally turns around and with a fairly put-out sigh he goes to collect John's laptop from him. Sherlock's is closer, it's right next to his chair, but John's already got the email open.

"Give it here," he says, leaving no room for argument, all but snatching it away from him and collapsing down in his chair to read through the email himself and begin to dig.