From a man who has been in the same "awful" situation that the Millane family now find themselves in, Tim Blackman is encouraging the family to "keep strong for Grace".
Father of deceased Lucie Blackman, 21, who went missing in Japan in 2000 and was later found dismembered in a beach cave, Blackman is also the founder of the Lucie Blackman Trust, which supports Brits missing abroad, and has also been helping Grace's family throughout.
Grace Millane embarked on a year-long world travel experience and arrived in New Zealand on November 2, but hasn't been heard from since last Saturday December 1, the eve of her 22nd birthday.
Mr Blackman says that Grace's case and his daughter Lucie's cases share some similarities: both girls were travelling overseas, both were in their early 20's and had great communication with family up until their disappearances, - and the advantage the Lucie Blackman Trust has is that New Zealand is an English speaking country.
"Communications have been much quicker and we're much more able to keep tabs on what's happening," Tim Blackman said in an interview with the BBC overnight.
Drawing on his own experience when he was in Japan looking for his daughter Lucie, Mr Blackamn says "you can't understate the level of shock that this produces".
"They will be absolutely terrified. They will be really suffering from this feeling of shock, but at the same time, will be holding onto the hope that some good news will come through soon."
Mr Blackman's message to Grace's family, at this time, is to hold onto the thread of optimism.
"Keep hold of that golden thread of hope.
"Just as there is no evidence that she is alive and well, there is no evidence that anything has tragically happened to her.
"I'm really hoping for them that they keep strong for Grace."
Grace's father has since arrived in Auckland, and in a statement, appealed to anybody who has seen, spoken to, or come into contact with Grace over the last few days, to come forward with any detail, no matter how small, and contact the investigation team.
She was last seen on CCTV footage at 9.41pm last Saturday, outside Queen Street's City Life Hotel with a man, who police described as a person of interest.
Anyone with information on Grace's whereabouts is urged to contact the Auckland Investigation team on 0800 676 255.
Alternatively, call the Lucie Blackman Trust on 44 (0) 1983 718802.