Two years passed. Successive intakes of air cadets qualified, got their 'wings', were 'polished' by Biggles and then moved on – mostly to be commissioned officers policing the Empire. Raymond continued to ask Biggles to do intelligence work – he found it difficult not to call on someone who was so much more than just skilled and efficient. By 1925, now 26 years old, Biggles was becoming more confident, and harder. Although not forgotten, he had come to terms with the trauma of 1918, gradually pushing it out of his consciousness. He had grown up.

From time to time, some occasion, some article in the paper, a comment in a conversation, something would remind him of Algy, and he'd wonder how he was. Algy was still playing tennis, that was clear from reports in the paper, and was to be seen occasionally in society photographs, usually accompanied by some suitable lady friend. Biggles had not communicated with the Lacey household since the end of the war. He was committed to his conviction that Algy was better off without him and he had no intention of getting involved with any of the Laceys ever again. But he noticed that Algy hadn't yet married, nor settled down.

In the summer of 1926, Biggles was assigned to an intelligence job in Monte Carlo to investigate the machinations of a group of Nazi sympathisers and trouble-makers, thought to be involved in illegal financial deals, and getting in and out of the area by air. He was given a false identity and gained access to the group with the help of another British agent, Mark Slater.

Biggles' German was by now near perfect and with fair hair, although Mark had said "pity you haven't got blue eyes too", he found it easy enough to pass as a German who had been in America for a number of years. The job ought not to have been difficult but it became apparent to both Mark and Biggles that another organisation was at work, not against the British but against the Nazi group. This was a complication.

Another complication was that the annual tennis tournament was taking place in Monte Carlo, and Algy was there, partnering Boris Zarrill as usual. Not only that, it turned out that Algy was staying at Boris' flat, just a few streets away from the hotel where Mark and Biggles were staying. Biggles worried that they might run into each other and that Algy might inadvertently give him away. He thought of trying to warn Algy, but as a new member of the Nazi group, Biggles was being closely watched. If any of the group knew about Algy's war record, and by chance connected the two of them the results could be disastrous. He hesitated, but in the end did nothing, expecting that he could easily avoid the tennis social set.

It was nearly a week later when he found out about the plot. He was now in a quandary. In air combat in France, they had done their utmost to watch out for each other – Biggles had never knowingly abandoned Algy in the face of danger.

In Palestine in 1918, serving as a double agent behind German lines, faced with what he thought was Algy's Camel attacking the German bomber he was flying, he put his mission at risk to warn Algy. "I got away with it that time," he mused "because the red Very light was a combat manoeuvre signal which the German flyers recognised and I got credit for." "But what on earth am I to do now?" He racked his brain desperately. "If I give them reason to suspect me, bang goes the job, and maybe Mark's safety too since he recommended me."

His problem was how to maintain his undercover identity and yet prevent Boris and probably Algy too from certain death? He wasn't unduly worried about Boris who he had never met, but the strong probability of Algy being with Boris in his flat on the afternoon in question filled him with horror.

He wondered whether he could shake off his shadow, but that in itself might be viewed with suspicion. The only solution he could think of was a desperate one but he could think of no alternative; its success would depend on Algy's co-operation.

On the afternoon of the operation, the first thing he had to do was to find out whether Algy was there or not. Biggles sauntered casually from his hotel to Boris' flat and rang the doorbell. Light footsteps sounded on the stairs and Algy opened the door. Out of the corner of his eye, Biggles saw his shadow melt into the darkness of a doorway.

Algy stared at him, open-mouthed "Biggles, whatever are you doing here? You're the last person I expected to see!"

"Can I come in?"

"Yes of course – come on up. I'm the only one in at present. I'm waiting for a chap from the tennis club because Boris couldn't make it this afternoon."

Biggles followed Algy up the stairs to the living room. "Algy, there's a problem," he started, "I can't explain everything now, but there's a group, up to no good, Nazi-based, and I'm supposed to be part of it – I'm trying to find out exactly what's going on."

Algy blinked at him in amazement "What on earth are you doing here then?"

"That's the problem." Biggles went on urgently "I don't know why yet, but they are out to get Boris, and they are planning to bomb this flat somehow, this afternoon – timed for 3 p.m. I was afraid you'd be here, and you are. I was afraid you'd be killed. You've got to get out before the bomb goes off, and warn Boris if you can."

Algy stared at him unbelievingly "This sounds like the worst sort of cheap thriller. I take it you're not making it up?"

"No!" Biggles was exasperated "Of course not. And the other problem is, I've got to have an excuse for coming here and both of us leaving."

"Why?"

"There's a chap watching me – he'll report back to the group and they'll want to know why I was here and what I was doing; especially if Boris isn't here when the bomb goes up. They are expecting him to be here – it's been arranged that he'll be here."

Algy shook his head "sounds a crazy business to me."

"Yes I can see it looks like that." Biggles looked Algy straight in the face "Algy, there's something you have to do for me".

"Yes, of course. What?"

"Shoot me."

"What! Are you off your rocker?" Algy couldn't believe that he'd heard Biggles correctly.

"Just something slight," Biggles snapped impatiently. I shouldn't have come here, I've been followed – I always am. I'll have blown my cover; I may have endangered a colleague. But there was no way I could stand by and risk you being killed."

He explained, "If you wound me slightly, somewhere not important, then run for it, I should be able to convince them I was on to something, but messed up. I have to be able to continue in the job without suspicion."

Algy blinked, still reeling from shock. A surge of anger went through him: "Don't tell me," he snarled, "one of Raymond's cock-eyed schemes. Biggles smiled faintly. He met Algy's eyes again "Once," he said quietly, " we had a commitment."

Algy stiffened, "Yes," he replied slowly. "Yes, we did, we do, well I still do… But that commitment does not, I repeat, does not extend to me shooting you."

"Would you rather that they did?" Biggles enquired evenly.

"Are you seriously telling me there's no other way?"

"If there were, would I be asking you?"

"So," Algy spoke harshly "which bit of you do you not need? Your head probably," he added sarcastically.

"Algy please, I…" They were interrupted by a loud explosion; the whole house shook and bits of plaster fell off the ceiling. There was a brief silence followed by the crackle of fire.

Outside there was a scream "Mon Dieu, le feu!" In voluble French, the cry was taken up by others.

Biggles and Algy stared at each other, dumbfounded. Biggles moved first – he opened the living room door and dashed to the top of the stairs. The whole of the front ground floor of the house was ablaze and their escape down the stairs was cut off. Biggles backed away and slammed the door shut. There was a crash as something hit the upstairs back window and splintered the glass.

"Algy, Bigglesworth – over here, quick!" They both spun round. A man teetering on the topmost rung of a wooden ladder was knocking out the remaining glass from the window frame.

"Boris! What on earth…?" cried Algy.

"No time to talk, over here, fast."

"You first" Biggles ordered Algy. "Don't waste time arguing," snapped Boris. The ladder was precariously placed and moved frighteningly as the last man down, Biggles, put his foot on the top rung, but it held in place and he reached the ground safely.

Boris thrust the ladder through the back ground-floor window, then before Biggles and Algy's astonished gaze, Boris and another man dragged in two bodies after it. Boris pushed them away "That car over there. Go... Now!"

They obeyed, falling into the back seat of an ancient Citroën as Boris flung a grenade after the ladder, then leapt into the car beside the driver. "Allez!" he screamed and the driver put his foot on the accelerator.

The car sped away down a maze of back streets. Once Boris was sure they were not being followed, he muttered to the driver and the car slowed down to a more reasonable speed, eventually driving up a steep hill and in at a concealed entrance to what was obviously an expensive private residence.

Inside, Biggles faced Boris angrily. "What's the idea? What's going on?"

"I might ask you the same thing," said Boris coldly. "What were you doing in my flat?"

Biggles drew a deep breath. He wondered how much Boris knew, and how much it was safe to tell him. "Look, thanks for getting us out of there but I don't see how you fit into the picture unless…" Biggles broke off, staring "Of course, how stupid of me. You are part of the group acting against the Nazis."

Boris smiled faintly "I am the leader of the group. And you, I believe, are working for British Intelligence."

"Yes."

"So, I repeat, what were you doing in my flat?"

"I'm working undercover in this Nazi outfit. I knew they were going to blow up your flat today. They arranged for you to be there this afternoon to sort out something with the club secretary. He's one of them. But Algy told me you couldn't make it and sent him to explain. The chap from the club never intended to show up. I couldn't let them blow up Algy – I hoped to warn him and I had a plan to persuade them I had just messed it up, but they acted faster than I expected."

Boris looked at him thoughtfully "Is that so? Well, all things considered, you'd better not mention this incident in your final report." He paused and considered. "Actually though, you had no need to worry. We had everything under control – we knew about it. We, er, removed the chap who was shadowing you, and the secretary, and we left them in the flat – as you probably noticed. Nobody in the group will ever know you were there if you get back to your hotel quickly. Anton will drop you off – in fact, you'd better get moving now."

He turned to Algy "Algy, you can stay here, they are not interested in you. You'll be safe." Boris looked sideways at Biggles, then suspiciously at Algy. "How come my tennis partner knows a British intelligence agent?"

"We are cousins," explained Algy "and we were in France together, in the RFC."

"Ah, the pilot friend you talked about! I ought to have remembered the name, it's distinctive enough. Don't worry," Boris looked at Biggles with some amusement "he didn't say anything too dreadful about you!"

Biggles was still wondering about the afternoon's events. He hesitated, "Did you set off that explosion then?"

"Yes. It was a controlled explosion, I assure you. We are used to doing that sort of thing."

Biggles didn't say anything. He was thinking that it hadn't really been that controlled; and suppose Algy had fallen off the ladder. He followed Anton down to the car.

Biggles gave Mark an edited version of the day's events although he had the uncomfortable feeling that Mark realised that there was more to it than he had said. However, it turned out that Mark knew about Boris Zarill. He had been mentioned more than once in connection with an underground group who had meted out punishment to spies and collaborators after the end of the war, so Mark wasn't surprised to hear of his involvement.

Later, Biggles and Boris met again, secretly. Biggles pointed out the danger and stupidity of Boris' group acting separately from the British, and Boris reluctantly agreed they should collaborate. As Biggles said to Algy later "He almost seemed to take it as a personal affront that we were muscling in on what he regarded as his territory."

Having got a working agreement, it was just a question of time before the loose ends were tied up and the group were, as Boris succinctly put it, 'dealt with'. Biggles knew that things hadn't been done in the way that Raymond and his superiors would have liked, but there really had not been a choice and at least there was no longer an immediate threat.