"I'm afraid it's cancer," is the first line of James Mok Lai-yan's The Challenge.

It is a story of four children - Adam, Aaron, Sarah and Sophie - who travel through time to 2086 to find a cure for their mother's cancer, a medicine that comes in an aerosol bottle.

James' mother, Rina Hui Yee-man, was startled. "When I first read the first sentence, I went: 'What? You wrote about cancer?'"

Like boys of his age, James grew up reading about spies like Alex Rider or adventurers such as the Pevensie siblings.

But in the end, it was his family that inspired him.

His mother is a medical oncologist specializing in breast and lung cancer. James lost both his maternal grandparents to incurable diseases so he developed a great interest in cancer from an early age.

One day, he hopes to find the cure.

"Every year we are getting closer to finding the cure for cancer," he says. "We know how to tackle it. We just need the technology or someone needs a bright idea."

Hong Kong-born James is now 17 and at a secondary school in England. His next challenge in life is to follow his father Edwin Mok Wah-sing's footsteps - go to Oxford and study biomedical sciences before pursuing a medical degree.

Though he wrote The Challenge seven years ago, it was released only this month. The family had planned to publish the book but put the plan on the backburner until they chanced upon it again while moving house two years ago.

They decided to send it in for publication but it took some time before someone in Sydney could translate it into Chinese.

The novel is partly autobiographical, with the four characters engaged in James' different interests - swimming, archery, chess, music, art and tennis."I was on a soul-searching journey while writing this novel," James says.

The characters have gone through challenges that call for perseverance, patience, humility and trust. James says that in reality, these are the virtues he needs to be a better person.

In particular, he has to develop perseverence if he wants to maintain his standards at the nationals. He almost gave up swimming when it proved to be so demanding.

Love is another major theme that weaves through the story. "I am most pleased with the ending of the novel, which affirms eternal love," he says, referring to his quote from 1 Corinthians 13:4-8.

"The contrast between the novel's beginning and end suggests hope even in the most desperate situations."

James says he might put the four protagonists back in time again for another adventure.

Looking back, James has indeed experienced a great challenge, both in writing and self-exploration, and he encourages his readers to follow suit.

"My late grandfather enlightened me with the saying that taking up challenges would lead to a big leap," he says, referring to his late paternal grandfather Mok Hing-yiu, a philanthropist and distinguished physician.

"I am very proud of James," says his mother.

The Challenge is currently selling for HK$68 in both Chinese and English.

Following the philanthropic example of his grandfather, James will be donating the profits to I-Care, a community charity program run by the Chinese University of Hong Kong.

Professor Joseph Jao-yiu Sung, Chinese University president and vice chancellor, is delighted.

"This is a story of love," he says. "This is about courage. It is about selflessness. This is in line with our goals.

"The essence of the I-CARE program is not to carry out mega projects with a few selected students, but to cultivate their humanitarian spirit and enhance their social awareness."

I-Care was inaugurated last September. It has supported around 200 university students who are involved in community work - serving the elderly, disabled or new migrants in Hong Kong, and helping the needy in the mainland, Africa and Vietnam.