Police may be close to finding body of missing mum Carlie Sinclair

Police believe they're on the verge of finding the body Stuart Park mum Carlie Sinclair 18 months after she vanished.

Officers are looking for a shallow grave at Berry Springs, and have arrested Ms Sinclair's former partner Danny Deacon on suspicion of murder.

Deacon has always been the chief suspect in Ms Sinclair's disappearance and this morning major crime detectives swooped, marching him to an unmarked police car at Tipperary Waters before he was frisked and arrested.

Among his possessions police seized a large amount of cash.

"The team of detectives that have been involved in this were steely in their determination," NT Police Commissioner John McRoberts said.

"They were professional in every thing they did, purely because they were not satisfied that Ms Sinclair had simply disappeared,"

The breakthrough that led to this moment came last night, when Deacon made an unexplained trip to the territory from his new home in Perth.

And where he came when he allegedly arrived – dense bushland in Berry Springs – is tonight being closely guarded by Northern Territory Police.

"Based on the information we have, including comments made by the man, we are very confident we know where Carlie is, although it will take us some hours and possibly, not even until tomorrow to be able to tell her family we have in fact confirmed her identity, and where she is," Mr McRoberts said.

For Ms Sinclair's tormented mother Marlene, her worst fears were right.

"I just want to bring Carlie home and give her a proper burial," she told 9NEWS.

Tonight she will make the painful journey from Melbourne, while her dad Rob and brother Kristian will come from Brisbane.

Danny Deacon remains in custody and has not yet been charged.