A boy who talks to Jesus. A deluge of frogs. A beautiful girl with a leather leg. A woman suspected of being a witch. They're all part of The Book of Everything, Canberra Repertory Society's next production.

Former Canberran turned professional actor-director Ed Wightman has returned to his old stamping ground for the play, his second directorial role with Rep after The Memory of Water last year.

The Book of Everything - adapted by Australian playwright Richard Tulloch - is set in Amsterdam in the summer of 1951. ''It's ostensibly about a young boy growing up in a violent, repressively religious household,'' Wightman says.

Young Thomas (played by Lachlan Ruffy) squabbles with his older sister Margot (Madeline Kennedy) whom he says is ''dumb as an onion'', is friends with Eliza (Tamina Koehne-Drube) who has a leather leg that creaks when she walks, and wonders about the neighbour, Mrs van Amersfoort (Helen Vaughan-Roberts), who is rumoured to be a witch.

His father (Jerry Hearn) is a stern, tyrannical man who beats Thomas and his mother (Lainie Hart) and reads to the family from the Bible. This forms the basis of many of Thomas' visions and daydreams. He sees things nobody else does, from Jesus (Miles Thompson) to the plagues of Egypt. And he writes it all down in his book that will, as the title says, explain everything.

Wightman did a lot of acting in Canberra - including Rep - and graduated from ANU before going on to study at the London Academy of Music and Dramatic Art. He's worked with many prominent Australian theatre companies including Bell Shakespeare and the Sydney and Melbourne Theatre companies and saw the original Australian production of The Book of Everything at Belvoir Theatre in 2010.

''I thought it was really special, really, really wonderful.''

Audiences and critics did, too, both here and in New York, where it toured.

For his production, Wightman says getting the tone of the play right is important - although it focuses on a child and his vision of the world, it's not a children's show, even as it reminds us what vivid imaginations children have.

''It's whimsical and very warm-hearted but serious as well. It's about how you have to live with yourself and find the courage to conquer your fears.''

Wightman says The Book of Everything is ''a play for all ages but not for young children''. It doesn't hold back from the darker aspects of its story and characters, yet it isn't a doom-laden piece but a hopeful one with plenty of humour and life.

''The play would be too heavy if it didn't find that lighter tone.''

Poignantly, one of the things Thomas writes in his book is his greatest determination: ''When I grow up, I'm going to be happy.''

Wightman and his production team have taken their cue from the fact the story is told from the perspective of a child.

''Andrew Kay's set design is as if it could've been done by a nine-year-old boy.''

All the child characters in the play are performed by adults - partly because the sophistication of the material required a certain level of experience and partly in keeping with the playful nature of the piece.

''There's a guy playing a dog.''

The director says he cast Ruffy for his talent rather than his age.

''He has a youthful energy and a wonderful playfulness that really suit the role.''

Ruffy is 22 going on 23. But as Thomas he's playing a character who is nine going on 10.

''He's very adamant that he's nearly 10,'' Ruffy says.

It's a challenge, especially since he's the only actor who plays one character throughout the play, but Ruffy is up for it.

''A lot of it is just having to commit to it. If you're just going in with a high voice and a lot of energy it doesn't really work. I didn't want to phone it in,'' he says.

This is Ruffy's fifth show in 2013. He's played many parts since he began acting 10 years ago and says The Book of Everything is ''the most beautiful thing I've ever done. It's gorgeous, it's honest … it's got real truth to it.''

Ruffy has been cast in adult roles, such as the sleazy Eurobeat co-host Serge - ''he was a little too adult'' - but is still being cast younger than his age.

''I played a 15-year-old last year [in Lost in Yonkers] and a nine-year-old this year … It would be nice to be cast as a grown-up once in a while.''