When mum Jenny Huddart and dad Adam Walker noticed a bruise on their baby's eyelid they put it down to her moving around more. She must've hit herself while playing with a toy they thought.
But the bruise continued to grow, eventually pushing her eye out of shape. It was then that they knew something was wrong and took her to the doctors.
Shortly after Easter, the family was told Harper has a rare form of cancer known as Neuroblastoma, a condition that affects around only 100 children per year. Mum Jenny told the Manchester Evening News: "Harper was born with hip dysplasia and was in a cast until last December and started moving more after that.
"We noticed in mid-February a little black dot near her eye but because she had been starting to move around more we thought she'd just hit herself with a toy. It started changing a bit but we thought maybe she had just rubbed it. But, then we noticed her eye starting to move up, like she had a lazy eye, and we took her to the doctors.
"At first the doctor wasn't concerned and said to come back in two weeks if it hadn't gone but by that point it would have been five weeks. The day after we called to get a referral to an eye specialist but that was going to take another week as it had kept changing shape so we called 111 who told us to go to Salford Royal.
"They straight away told us we needed more tests but they don't have the right eye specialists at that hospital so sent us to Manchester Eye Hospital. We went in on Good Friday and Harper was admitted for tests and went home.
"On the Monday we got the phone call from the doctor asking us to go in where we were told they had found a lump in her sinuses. And then a biopsy confirmed and we were told Harper had stage four cancer. Further tests showed it was an aggressive form of Neuroblastoma."
On being told this news Jenny said: "It was as if it wasn't happening. We felt numb. We started Googling things even though you're not supposed to and saw the stats for this which aren't great.
"Apparently it's something that originally grows while she was a foetus, but there was no way of knowing about it until the little bruise appeared. We were told by people who've been doctors in this area for 33 years that they've never seen it present like this, we knew something wasn't right when it started to move her eye. It's just awful."
Baby Harper is now undergoing an 18-week treatment with chemotherapy and surgery, and will receive stem cell treatment and radiotherapy. The family of seven is hoping to get Harper treatment at the pioneering Sloan Kettering cancer centre in New York to give her a new form of treatment that increases her chances of survival up to 60 to 70 per cent. However, the treatment alone for this costs more than £280,000 with multiple trips over to the States needed for this.
Dad Adam set-up a JustGiving page yesterday where they are aiming to raise up to £300,000 to help fund this potentially life-saving treatment. In this short space of time it has raised nearly £13,000 with Jenny saying the family are "overwhelmed" by the support they have received so far.
To read and keep up with the full fundraiser, visit the Just Giving page here.