First: what did and didn't just happen

What happened: your child came to believe there is one God, the God of Abraham, and that Muhammad was His final messenger, and they said so out loud. What did not happen: they did not join a race or a foreign country, renounce you, sign anything, or hand their life to a movement. There is no organisation with a claim on them, no clergy with authority over them, and no doctrine telling them to leave you; you will read below what their new faith commands about you specifically.

It is also, in every likelihood, not about you, not a rebellion, and not a phase entered lightly: conversion to Islam in the West usually follows months or years of private reading, precisely because the convert knows this conversation will be hard. The person who told you was almost certainly more frightened of losing you than of anything else in the process.

What their religion says about you

This may be the most useful thing on this page. The Quran binds kindness to parents into the same sentence as the worship of God: "Your Lord has decreed that you worship none but Him, and be excellent to parents" (17:23), and it addresses your exact situation directly: even if parents oppose the child's faith, the command stands, "accompany them in this world with kindness" (31:15). Muhammad taught that Paradise lies at the mother's feet and that keeping family ties is a condition of faith itself. Your child's new religion has, in effect, made being good to you an act of worship. Many parents find, a year or two on, a child who calls more, argues less, and shows up better, and converts will tell you the religion is why.

The fears, honestly addressed

• "The headlines." You've absorbed decades of the worst 0.01% presented as the norm. The teaching itself, on violence, on women, on how Muslims must treat non-Muslims including you, is laid out plainly on this site (common questions, the hard questions, nothing dodged); judge your child's faith by what it teaches and by your child, not by criminals its own scholars condemn.
• "Have they been radicalised?" The honest markers run opposite to what you fear: mainstream Islam pulls converts toward mosques, scholarship, family duty, and boring respectability. If your child is praying, working, and telling you to drive safely, that is what normal looks like. (Isolation from all family and community is a warning sign in any group, and mainstream Muslim communities are allies against it, not causes of it.)
• "For a partner?" Sometimes a partner opens the door; sincere converts walk through it for themselves, and Islam itself holds that conversion for a person, without belief, doesn't count. Time makes the sincerity obvious either way.
• "Did we fail?" No. They took the God, the seriousness, and usually the values you raised them with, and followed them somewhere unexpected. Many converts describe it as completing their upbringing, not repudiating it; Muslims revere Jesus, Moses, and the Bible's prophets, so more of your inheritance survives than you currently think.
• "Christmas dinner? Sunday lunch?" Still on. They'll skip the wine and need the stuffing pork-free; they have not been commanded to shun your table, and being present with family is the strong default their scholars urge. Ask them what works; the conversation itself heals things.

What helps (from families further down this road)

• Let the first reaction be forgiven, in both directions. Day one is rarely anyone's best performance. The relationship is measured in years.
• Ask questions instead of Googling alone at 2am. "What made you sure?" honours them; the internet's worst corners will not.
• Keep every ritual you share: the phone calls, the fishing trips, the birthday cake. Continuity is the message they're desperate to receive from you.
• Meet one of their Muslim friends, or accept the Eid dinner invitation, when you're ready. Abstractions frighten; people mostly don't.
• And grieve if you need to. Something did change, and pretending otherwise helps no one. Grief and love can share a table; they usually do.

Curious what they actually believe now? The gentlest introduction is the journey, and what their daily life looks like is here. You may recognise more of your child in it than you expect.