Imagine if you threw a party and no one showed up.

For Idil Eser, Director of Amnesty International in Turkey, there is no danger of that tomorrow, 14 October, as thousands of people are expected to gather to celebrate her birthday.

Only one person will be missing: Idil herself.

Instead of taking part in one of the more than 200 birthday parties that are taking place in 27 countries, Idil will be spending her birthday in the highest security section of Turkey’s highest security prison.

She was arrested, alongside nine other human rights defenders, on terrorism charges just over 100 days ago. Last Sunday, in an alarming development, a Turkish prosecutor filed an indictment calling for jail terms of up to 15 years for the group – known as the ‘Istanbul 10’.

The indictment also suggested the same treatment for Amnesty International’s Turkey Chair, Taner Kiliç, who was arrested a month before Idil on similarly ridiculous charges.

For more than two months after her arrest, Idil (who has no parents, siblings or children) was not allowed personal visitors – an emergency law makes only immediate family eligible visitors. Despite the avalanche of birthday cards and messages sent to Amnesty International by well-wishers, she is still not allowed to receive mail.

The austere environment of Silivri prison – the largest penal complex in Europe – is a far cry from how Idil used to spend her birthday. Normally, she is in one of her favourite restaurants, sharing food, wine and laughter with friends, before going home to her cosy flat and three beloved cats.

She admits that her detention has been very hard, sharing a cell with another woman and unable to speak to the others who were arrested alongside her, such as Özlem Dalkıran.

‘Özlem is only three doors away but if I want to find out anything about her I have to try and find out in the newspapers,’ she explained last month.

But Idil’s spirit has not been broken. ‘I have not committed any crime other than defending human rights,’ she says. ‘My time in prison has made me more committed to standing up for my values. I will not compromise them.’

Idil is aware that she and the others are behind bars as part of an orchestrated attempt to silence dissenting voices in Turkey. Since the failed coup attempt in July 2016, more than 50,000 people remanded in prison and more than 100,000 public sector employees summarily dismissed.

In the last year, at least 156 media outlets have been shut down and an estimated 2,500 journalists and other media workers have lost their jobs. More than 140 journalists and media workers are imprisoned, pending trial.

Rounding up human rights defenders was clearly intended to send a message that dissent will not be tolerated. But the courage of Idil and her colleagues and the support they have garnered around the world has sent a brighter message: critical voices cannot be silenced.

On 14 October, there will be birthday parties in towns and cities across the globe, from the European Parliament to a makeshift prison in Madrid. Full-size cardboard cut-outs of Idil will join in the festivities to highlight her absence.

Idil is not someone who craves the spotlight. What drives her is the desire to make a positive difference to people’s lives and to the increase awareness of the importance of human rights in Turkey.

In a letter to her supporters last month, she was in characteristically good spirits but admitted: ‘I miss music, my cats, being with my friends and being at my work.’

On this day people around the world are thinking about Idil and making a collective birthday wish. That wish is for the Turkish authorities to immediately and unconditionally release the Istanbul 10 and end the post-coup crackdown that is ravaging the country.

Fotis Filippou is Amnesty International’s Director of Campaigns for Europe.