Which raises the question...

Hitchcock's movies pose more questions than they answer - BBC News Online goes in search of the facts behind the films.

Vertigo (1958)

Vertigo-prone cop James Stewart finds the rooftops of San Francisco too daunting. Off the force, Jim goes freelance to track a pal's wandering wife - only to fall obsessively in love with her.

Clinical Nurse Leader Jonathan Ash examines the case.

What is vertigo?

It's a phobia, a fear of heights. Sufferers avoid buildings over two storeys, air travel and even lifts. Just being up high causes anxiety, but many people feel more fear if they look down through windows.

What happens during a vertigo attack?

The normal range of anxiety symptoms - feeling hot, flushed or sweaty. Dizziness, nausea and blurred vision are also common. In severe cases, patients complain of depersonalisation - a feeling of distance from events around you.

What treatments are available?

We use exposure therapy - gradually getting patients to face their fear. People are encouraged to go further up staircases or across bridges during each session.

I Confess (1953)

After hearing the confession of a murderer, Catholic priest Montgomery Clift finds himself accused of the crime. Unable to reveal the real killer's identity without breaking the secrecy of the confessional, Clift battles with his faith.

Monsignor Kieran Conry comes clean.

What is the purpose of confession?

The act of confession is part of the sacrament of reconciliation. Sin damages our relationship with God and confession is a step in mending that relationship.

We confess to God through a priest. They may suggest forms of penance. A formal prayer of absolution is given to forgive the sins and help the rebuild the relationship.

What is the difference between crime and sin?

Crime is simply against the law. It is not sinful to park on a double yellow line. Sins are the things the Church considers morally wrong. You cannot sin by accident, or be forced to sin.

What if a murderer admitted their crime during confession?

Priests are bound to respect the confidentiality of the confessional. They cannot reveal what they hear, even to someone higher in the Church.

Psycho (1960)

Motel owner Anthony Perkins lives with his tyrannical "mother", quietly pursing his hobby - taxidermy - until runaway Janet Leigh draws his attentions.

"Animal Instincts" taxidermist Paul Draper fills in the gaps.

How do you go about stuffing a creature?

The body of the animal is skinned and measured. The skin is place in a tanning solution of chemicals, to fix the fur or feathers.

The skull is the only bone used. A wire spine is attached to this. U-shaped wires are added for the legs. Woodwool is wrapped around to create the form.

The body and face are posed and the skin is replaced. Glass eyes and ear stiffeners finish the process.

What's the strangest thing you've stuffed?

A human finger. Someone chopped it off by accident.

How long do stuffed animals last?

Well, 100 years is not unreasonable. If you take proper precautions, keep them away from damp and treat them with an insecticide.

The Lady Vanishes (1938)

A train speeds across pre-war Europe. When an elderly passenger goes missing Margaret Lockwood and Michael Redgrave are left scratching their heads.

Claire Ainsley of the National Missing Persons Helpline solves the mysteries.

How many people go missing?

There is no comprehensive national database. The estimated figure is that 250,000 go missing in the UK each year. The National Missing Persons Helpline receives more than 100,000 calls a year.

How long do you have to be away to count as missing?

The police definition is if you are out of contact for 24 hours. They search for vulnerable individuals - the under-18s, people with illnesses or those connected to a crime.

We draw a distinction between those who disappear by choice to start a new life. Our priority is find out if they are safe and well. We keep their whereabouts confidential.

Do most people turn up?

We have 20,000 unresolved cases registered, but the charity does clear up 70% of the disappearances we investigate.