Families of people killed and secretly buried will take part in a memorial walk at Stormont today.
The 14th annual All Souls Silent Walk for the Disappeared takes place at noon. Because of Covid-19 restrictions it will be on a smaller scale than normal.
Oliver McVeigh, whose brother Columba was murdered and secretly buried by the IRA in 1975, will lead the small group from Carson's statue to the steps of Parliament Buildings.
A black wreath with white lilies representing those who have yet to be found will be laid on the steps by Oliver. Three lilies will represent Joe Lynskey, Columba McVeigh and Robert Nairac.
A fourth white lily will be added for Lisa Dorrian, who disappeared in 2005. Her father John and sister Michelle will join the other families at Stormont.
Sandra Peake, chief executive of the WAVE Trauma Centre which has supported the Families of the Disappeared since 1995, said: "Because Lisa disappeared in 2005 her case could not be taken on by the Independent Commission for the Location of Victims' Remains (ICLVR) because the legislation governing the operation of the ICLVR means that it cannot accept cases that came after the Good Friday Agreement of April 1998.
"Gareth O'Connor, who disappeared in 2003 and whose body was recovered from Newry Canal in 2005, fell outside the ICLVR's remit for the same reason.
"The pain and grief of Lisa's family is profound and like the other families of the Disappeared their torment will continue until Lisa is brought home for Christian burial.
"We are glad John and Michelle will be with the other families and our thoughts and prayers are with them."
Fr Joe Gormley from Creggan will lead prayers while Fr Paul Turley, who cannot be present, will light candles of remembrance at noon in Clonard and will pray for the families.
Ms Peake added: "We hope and pray that soon all the families will receive the news they have waited so long to hear.
"In the meantime they will stand together in an unbreakable bond of solidarity and support."
Anyone with information about any of the three ICLVR outstanding cases should contact the ICLVR's confidential telephone number on 00800- 555 85500, email firstname.lastname@example.org or write to ICLVR, PO Box, 10827, Dublin 2.
Information about Lisa Dorrian can be passed to detectives working on the case on 101 or anonymously to the independent charity Crimestoppers on 0800 555 111.