Roots: Phone Booth The Doctor quotes from Thomas Jefferson ("I'm a great believer in luck...") Henry V "Discretion is the better part of valour" Comic serials ("and with one bound he was free")
Continuity: The [alien] parasite which invades Lauren and latches onto her spine resembles a metal worm or snake, about six inches long and with legs all along it; the Doctor believes that if not removed in time (within a day) it would have killed her and processed the raw material of her body, transforming her into a slug-like creature. At the hospital having made the fuss the Doctor recommends, Laura is successfully operated on and made by army officers (UNIT?) to sign the Official Secrets Act.
The Doctor in his investigation of his and Laura's coincidental crossed calls discovers traces of a very sophisticated bio-engineered virus transmitted by telephone. Having infected a person, it causes them to make subconscious mistakes the next time they use a telephone, dialling a wrong number. The virus also orchestrates coincidences so that the wrong number leads to a person who will either be of benefit to the original caller, or may need their help (as Laura has needed the Doctor's.) The virus then continues to spread until it dies naturally. The Doctor thinks the virus is military in origin and was intended for sleeper agents, enabling them to communicate with each other without carrying incriminating contact details, as well as put them in touch with strangers best placed to help them. If the virus was adapted, it could potentially be used to assassinate someone over the phone.
The Doctor doesn't believe in fate. He is gaoled at Green Street station under the name of Dr John Smith. The Doctor is based in the same area as Lauren conducting other business when her infection with the 'coincidence' virus engages his attention - it is not revealed what his primary reason for being in England in 1974 is (although it does lead him to being gaoled briefly on a charge of trespass). He declares that he has no phone and prefers to write letters. His policy is never to let cultures keep hold of advanced technology that they're not capable of handling.
A radio plays "Blue Starlight" by Steve Silver
Links: After Lauren's mention of a visit by an 'Army man' and a doctor the Doctor asks if the latter was tall with white hair and flamboyant clothes (i.e. his third incarnation).
QV: 'The Viyran Strand'
Location: Somewhere in England (ooh let's say... London), 1974
The Bottom Line: "You were right. If it was all just luck, it wouldn't mean anything".
An economy of script and character brings out one of Robson's best audios. Funny without being silly, touching without being schmaltzy - even the continuity references aren't overdone (or indeed what the initially seem to be). In order to follow the story you needn't know any more about the Doctor than Laura does. Simple genius.