A man was stabbed to death in broad daylight following an argument on a platform at a busy railway station.
Emergency services sped to the scene of the incident at about 10am.
The victim, a man in his 40s, was rushed to hospital by paramedics but died a short while later.
A murder investigation has been launched and part of the station cordoned off while investigations take place.
A 29-year-old man has been arrested on suspicion of murder.
He was initially taken to hospital for treatment to a hand injury.
Senior Investigating Officer DCI Paul Langley, said: “This was an attack on a man in broad daylight at a busy station in Devon.
"We are now working to identify the man and inform his family.
“At this time, it is believed the two men knew each other and had an argument at the station, which resulted in one of the men assaulting the other.
“The victim was taken to hospital but he sadly died despite the best efforts of the medical teams.
“We are now asking anyone who may have been at Plymouth station this morning and witnessed what happened to come forward and speak to us. Any information, no matter how small, could prove vital in our enquiries.”
Anyone with any information is asked to get in touch by sending a text to 61016 or by calling 0800 40 50 40 quoting reference 159 of 08/08/2017. Alternatively, ring Crimestoppers anonymously on 0800 555 111.
