First Light Rising: Kindred of Old

My name is Saskia. On 29 July 2047, I lost a friend.
As a teenager, Tom Wright made claims nobody believed. We were all wrong. When
Tom turned twenty-four, MI5 uncovered the truth - and set the world on fire: Tom was
no longer ageing.
Earth was not ready for an immortal. World powers tried to control him, hide him, and
weaponise the secret he carried. As governments closed in and humanity edged
towards war, I brokered the only truce left: Tom would leave Earth on the Icarus,
humankind's first interstellar mission, travelling 150 years into the future.
On 29 July 2047, Tom left Earth.
Six months later, the Icarus is found empty.
The world believes Tom chose oblivion, stepping out of the ship and into the void.
What it does not know is that he changed the mission.
Only I know the truth: immortality is not his only secret.