Murder detectives hunting the killer of a man whose body was found in a canal have released CCTV footage of a man who may have "critical" information.
Darren Round, 48, who was discovered near Masshouse Lane, Kings Norton, Birmingham, on 15 February 2020, had suffered severe facial injuries.
West Midlands Police said his injuries had been "consistent with assault" before he had gone into the water.
Mr Round's mother said she did not want to die not knowing what had happened.
Sheila Round said: "He said 'Ta'ra mum, I'll see you later'. And that was it.
"There's nothing worse than losing your only child. I don't want to die not knowing what that happened that night."
He left the home he shared with her in Kings Norton on 14 February and was wearing a blue coat and carrying a rucksack on his back.
CCTV footage shows him walking along the canal close to Wharf Road Bridge towards Shannon Tunnel at about 12:40 GMT.
And Det Supt Scott Griffiths said it was believed he had entered the water at 01:50, when his mobile phone stopped sending data.
Talking to BBC Crimewatch, Det Supt Griffiths said detectives had pieced together his movements and knew Mr Round had withdrawn money from a cash machine at the post office in Kings Norton Green.
Mr Round bought alcohol from an off-licence before making the nearly five-mile walk into the city centre along canal towpaths.
The man in the CCTV footage is about 5ft 6in (1.6m) tall and is seen with "distinctive" trainers with small reflective panels, what officers believe is a light-coloured tracksuit and carried a "man bag".
Det Supt Griffiths said: "None of Darren's possessions were taken and we can find no motive for anyone to have subjected him to such a brutal beating, but we remain determined to establish exactly what happened.
"We have conducted extensive work on CCTV and there is a man we'd like to speak to who we have so far been unable to identify, as he may have information critical to our investigation."
Crimestoppers has offered a reward of £10,000 for information leading to the conviction of those responsible for Mr Round's death.