It's early afternoon on September 16, 1986, at the Lawrence Berkeley Laboratory in California.

Clifford Stoll sprints through the office, dashing past cubicles and startled colleagues.

A 36-year-old technician with a wild mess of dark curly hair, Cliff has just been alerted

to an unverified user inside Berkeley's computer network. Although their true identity is hidden,

Cliff knows who it is. It's the same hacker he's been chasing for almost a month.

Cliff bursts into the computer lab, squinting against the sudden, harsh white light.

All around him, terminals glow, printers chatter and disc drives rattle like washing machines.

Cliff grabs the phone beside his monitor and immediately dials Ron Vivir at Timnet,

the company that runs the international computer network used by Berkeley.

Gasping for breath, Cliff says the hacker is back.

He listens as Ron quickly contacts the local phone company to set up a trace.

Cliff then paces the lab, jerking to a halt whenever the phone cord yanks them back.

More people join in the call as the trace is followed from region to region, phone company to phone company.

Cliff struggles to follow the telecommunications jargon about rerouting codes, rotary PBX systems, and other technical details.

All he wants to know is if the

trace has weren't. That's when a woman with a thick southern drawl dials in. She explains the

hack is coming from Virginia, but to double check she needs to interrupt the connection for a second.

If the hacker is ejected from the system, they'll know they've traced the right line.

Cliff stares at his blue monitor, and sure enough, the hacker drops off.

Cliff lets out a cheer because they've got him this time.

They've figured out where the hacker is dialing in from.

Now they can finally find out who it is.

...