MADDIE Pulver took to the hockey field yesterday, determined to get on with her life as clues in the bizarre Sydney extortion case emerged.

An obscure book at the centre of the mysterious bomb hoax was on a recommended reading list for students at a school closely linked to the wealthy Pulver family.

A note attached to the fake bomb was signed "Dick Straun", who is the main character in the book, Tai-Pan.

Last year, students at Sydney Church of England Grammar, known as Shore, were encouraged to read the 1966 James Clavell novel.

Ms Pulver, 18, is in year 12 at the school's sister college Wenona, in North Sydney.

Maddie's brothers and many male friends are at Shore, where her father, Bill, also studied.

Robbery and Serious Crime Squad detectives are probing several new lines of inquiry that have emerged since the family were interviewed on Thursday night.

State Crime Commander David Hudson said: "We start our investigations wide and then we shrink them.

"Nothing is excluded which may assist us with our work.

"I am not commenting on our present situation, because it may compromise the investigation which we are conducting," Cmdr Hudson said.

The note attached to Maddie - which featured references to Tai-Pan - did not include instructions for a handover of money, but Det Supt Luke Moore confirmed a "demand" had been made.

Yesterday, the 18-year-old donned her shinpads and headed to Sydney's inner west for an inter-school hockey competition.

Leaving home in the company of her father, Bill, and mother, Belinda, soon before 9am, Maddie clearly relished the opportunity to catch up with teammates.

After laughing and chatting with friends in a warm-up session, watched by a slew of television crews, she took to the field for a spirited game.

Her team eventually went down 2-0, but she was commended for her determination in attending.

There were supportive cheers from the crowd, and her teammates patted her on the back as she returned to the change rooms.

Maddie said she had looked forward to rejoining her teammates, saying her friends had been a "very good pillar of support" following her ordeal.

"It will be good to be back to normal," the 18-year-old said.

Earlier, Maddie took advantage of the warmer weather, heading out for an early morning swim with a male friend about 8am.

It was the same friend who had comforted her on Friday night, cuddling and hugging her during a visit from school mates.

But it won't be all fun and games for Maddie in the weeks ahead.

As she tries to come to terms with her horror bomb hoax ordeal, she will also have to resume her studies for her HSC exams.

Along with her fellow year 12 classmates, Maddie had been scheduled to begin the tests last Thursday - the day after she was attacked while studying alone at her Mosman home.

Staff at Wenona postponed the exams in the wake of the attack, citing the distress the incident had caused all students.

It is believed the exams will go ahead this Thursday.

Former NSW Police assistant commissioner Clive Small said the Tai-Pan link to the school uncovered by the Sunday Herald Sun was a remarkable development that must be investigated.

"As a detective, you would examine all lines of inquiry, including the possibility this crime have been committed by school-aged youths," Mr Small said.

"The fact that it's on a school reading list would make it a significant line to follow."

The novel - which features graphic sex scenes - was listed as the number two recommendation on the April/May 2010 fiction list at the Shore senior library.

The "new fiction reading list" contained 37 books in its catalogue, which is available on the school's website.

Shore headmaster Tim Wright declined to comment when asked if police had visited the school to interview students who had borrowed the book from the library.

In a written statement, Mr Wright said the book was not part of the 2011 reading list for students, but was available at the school for loan.

"The book was not part of the school curriculum reading list but it might have been recommended to students by librarians," a school spokesman said.

"The book is available in the school library as it is in many public libraries."

Retired detective inspector Justin Chisholm said this was a lead that must be followed up.

"This would appear to be one of many obvious lines of inquiry," Mr Chisholm said.

"Investigators would obviously need to follow a range of leads, including the possibility of students in year 12 who, as part of their reading, read the book Tai-Pan, whose main character is Dick Struan.

"These incidents can often be anything from pranks gone wrong to legitimate hostage threats."

Days after the 10-hour ordeal, police were yet to shed any light on it.

The family has returned home. Police have not issued any warning to neighbours.

Maddie's father, Bill, said the family were worried.

"It's really scary this guy is still out there," he said.

"We just don't know where he is or what he's doing.

"We'd like to stay (at the house) and get this guy off the streets."

Mr Pulver said he had no clue about who would try to harm his family.

"No thoughts at all," he said. "We don't want to do anything to jeopardise the investigation. I know nothing.

"At the moment, we're just trying to get life back to normal," he said.

Mr Pulver said he was proud of his daughter's strength in the past days.

"She's just been amazing through this," he said.

Police have instructed the Pulver family not to conduct any formal media interviews and have closed ranks around the investigation to avoid any leaks.



THE MADDIE MYSTERY

1 Tai-Pan, the obscure James Clavell book at the centre of the "bomb necklace" drama, is on the reading list for students at the nearby private school, Sydney Church of England Grammar

2 Many of Maddie's male friends attend this private school which is known as Shore

3 Tai-Pan is available for loan from the Shore library

4 Maddie's dad, Bill Pulver, says it's "really scary this guy" is out there